As Cauncy said its a gutter sitting in a rail, that is generally level and runs around a 1/4 of the house perimeter, to 3 drains.
The original problem was that the downpipe fold/cut was done poorly; as in pic B.
Even with nothing "blocking" the gutter, it would still backfill as there was about a 3mm slit for the water to escape through, twice.
This overflowed the gutters into the eaves. I found a single leaf and a couple of roof screws totally blocking it.
(The builder came back to fix.. kinda)
I've added mesh to stop leaves and rocks* getting in.
So theoretically, I have resolved the gutter blocking issue...
Next step would be to replace the downpipe altogether with 90mm PVC.
Which should be easy enough.. I even have the paint to colour match.
Another option would be to put in some pissers.. essentially does the same thing as the slotted gutters. (Just sounds better) 
www.seabreeze.com.au/img/photos/other/13290653.jpg' />
As said, The hardieflex lining is hard against the window fin at the top. I cant get it to move at all.
The order of how it all went in would probably make it easier to understand.
So fuggit! I'm just going to cut in a vent.
2 Reasons:
1) Airflow; The hardieflex will dry out on its own but there has been mould growing on it, so it stays wet for a while.
2) If the gutter overflows again, it will drain out the vent rather than the windows 
*Rocks get dropped by the local crows, smooth round rocks from a house up the road, have no idea what they use them for?
Take your downpipes off
drill rivits out then cut back insides of downpipes so u have 10 - 15mm inside not 70
if your worried about them blocking up again cut overflow holes in gutter lower than the back of it
If your fascia and gutter has been installed properly it will overflow between the fascia and the back of the gutter. The gutter is usually hung on spring clips which have 6 or 7 teeth on them that clip on to a rolled edge at the top of the gutter back. Near the down pipes it should be clipped on to lowest tooth and midway between the downpipes it should be on the highest tooth giving fall to the downpipes. If it overflows it should come out somewhere near the downpipes being the lowest point and at this point the fascia will be about 40 or 50 mm above the top of the back of the gutter and so should not flow over and into the soffit.
This is of course assuming the fascia was installed level and that your house hasn't sunk in some areas.
Don't pull the soffit out, that will dry out in time just fix the fall in the gutter. 90 mm downpipes will be heaps better.
That gutter looks like its aluminium mobile rolled out of the back of a truck on site. The support system may be a little different but basic principals still apply. If you have a tile roof, you only have to slide a couple of tiles up to gain access to the soffit for what ever reason.
Have fun fixing it! I installed the crap for about 18 years and now avoid it as much as possible.
Select to expand quotecauncy said..
You can make the eave out of level, you just plum cut rafter lower down, it's just not our practice to do such and would be picked on by builder/ supervisor / client
Well it shouldn't be up to the chippy, this is an architect/accountant problem.
Select to expand quoterod_bunny said..
As Cauncy said its a gutter sitting in a rail, that is generally level and runs around a 1/4 of the house perimeter, to 3 drains.
The original problem was that the downpipe fold/cut was done poorly; as in pic B.
Even with nothing "blocking" the gutter, it would still backfill as there was about a 3mm slit for the water to escape through, twice.
This overflowed the gutters into the eaves. I found a single leaf and a couple of roof screws totally blocking it.
(The builder came back to fix.. kinda)
I've added mesh to stop leaves and rocks* getting in.
So theoretically, I have resolved the gutter blocking issue...
Next step would be to replace the downpipe altogether with 90mm PVC.
Which should be easy enough.. I even have the paint to colour match.
Another option would be to put in some pissers.. essentially does the same thing as the slotted gutters. (Just sounds better) www.seabreeze.com.au/img/photos/other/13290653.jpg' />
As said, The hardieflex lining is hard against the window fin at the top. I cant get it to move at all.
The order of how it all went in would probably make it easier to understand.
So fuggit! I'm just going to cut in a vent.
2 Reasons:
1) Airflow; The hardieflex will dry out on its own but there has been mould growing on it, so it stays wet for a while.
2) If the gutter overflows again, it will drain out the vent rather than the windows
*Rocks get dropped by the local crows, smooth round rocks from a house up the road, have no idea what they use them for?
You can fix the issue of flow from your original downpipes
you should have a rivet up near gutter, this is put in to hold up pipes to plumb up and clip back to wall
drill it out and release clips
drill out all rivets to pipe and cut off excess material which plumber has left in, but be sure that some is left to divert flow over joints, then re position and re rivet, or get a 90/45 converter to 90 stormwater and convert to pvc, this is what I have on my house but in class 4 ( thicker wall) the flow is massively increased,
Another important check
Is your water running to a tank/ drain/ etc as this may be blocked and causing the flow to back up and overflow,
ive seen this on a few jobs where flooding of eaves and cavitys have occurred
To be honest the whole industry especially project housing is to blame ,
Tradesmen tbh have little pride today in their workmanship as they're screwed on price from builders, I used to attend master builders meetings as a trades spokesperson in Perth
I was stunned to hear life expectancy of some new homes were 30/35 years
i work on houses in France in lacapelle marivale that had Roman numerals over the door, and were structurally sound, I call wa housing lego land, some areas are catastrophic with no imagination and little regard for energy efficiency or longevity in construction,
But most people drive that demand for cheap shidt housing
(Looks like something go hosed in the pics I put up) 
Replacing the downpipe with 90mm PVC would be easy enough
Even sits close to the wall.
I did think about the system backing up, theoretically it should have been flowing out of these but it wasn't.
Select to expand quotecauncy said..
To be honest the whole industry especially project housing is to blame ,
Tradesmen tbh have little pride today in their workmanship as they're screwed on price from builders, I used to attend master builders meetings as a trades spokesperson in Perth
I was stunned to hear life expectancy of some new homes were 30/35 years
i work on houses in France in lacapelle marivale that had Roman numerals over the door, and were structurally sound, I call wa housing lego land, some areas are catastrophic with no imagination and little regard for energy efficiency or longevity in construction,
But most people drive that demand for cheap shidt housing
Damn right Cauncy add to that people doing renos and owner/builders that buy/import the cheapest materials and use cheap labour and cover up the poor work 30years you would be lucky if it lasts that long.
There are builders that screw trades who in turn cut corners but at least the consumer gets a 4x2 with home theater and alfresco for $140K doesn't matter if the gutters leak back in the house.
There area some good builders around but from what I have seen it is a real if you can't beat them join them industry.
Select to expand quotecauncy said..
To be honest the whole industry especially project housing is to blame ,
I was stunned to hear life expectancy of some new homes were 30/35 years
Its not just housing... everything is built/designed to not last... how else can they sell you more? 
Needed a battery for my drill... quoted $200 from the Trade desk. or $80 online... Its 12 C cell batteries FFS. Even the batteries on their own are $9... EACH!
For the cost of 2 batteries I could have bought a new drill and impact driver set with 2 Li Ion batteries included? 
So, what happens with the perfectly good but powerless drill? Bin.
