Concentric fill not working properly

I've run into this problem tryin to use the Concentric fill pattern for the top/bottom layer.
It leaves a gap mid way of the top fill layer and I haven't got the slightest clue what causes it. I tried tweaking the models (2 similar cylindircal models have the same issue) and settings for the top fill layers. Changing the settings does effect this gap but only making it bigger or smaller, it never dissapears.

I wonder if anyone can point me in a direction I should be looking to fix this.

Arjan

It seems a strange pattern, but I think the issue is probably a result of the shape that is filled not being an exact multiple of the extrusion width. i.e. you cannot fill a space that is 10.5mm wide with concentric lines that are 1mm wide - it will have to leave a 0.5mm gap somewhere. Try changing the extrusion width by small amounts ("Print Settings">"Advanced") and see if you can find a width that results in the desired output.

Dave

That was my first thought and I tried tweaking it but it didn't help.
I tried again with smaller increments and I do get closer, but it still always leaves a gap. I tweaked it but between 94.8-96.2% it doesn't change and leaves are gap. I'm printing it now to see if it is acceptable.

For those who are interested or run into the same problem:

I ended up using 126.7% (gonna be different for every object) for the top solid infill extrusion setting.
Resulting in a very nice top finish with.

Turned out using the lower percentage I first tested creates a denser fill, messing it up completely because the nozzle keeps touching the previous layer.