I think this is related to the problem I have been having and noted in the "Wall thickness below STL thickness" thread. I have been able to get what I want with Slic3r. I hope that this is something that the Creator folks will be working on soon. I don't want to have to use Slic3r every time I have an object with thin walls.
I'm having the same problem of not getting a watertight top cap when printing in the high quality setting. I am familiar with the narrow wall problem, as RepG has the same inability to deal with thin walls. The work around for that is the same, set shell number to one and up your fill. Also design with this in mind. I've made a model that had a series of walls where each wall was thinner than its neighbor by .2mm. I then printed these with different extrusion widths and wall numbers to see what an ideal design, FFF combo works .
All this being said I still haven't gotten a nice top surface on anything yet using high resolution settings. This should be the simplest of fixes, and I haven't won yet......
As explained before there isn't room for 3 walls in that section so it only prints 2 and and leaves a gap. This is mostly user error in not understanding the software. To help these people I would maybe suggest a software option to reduce the number of walls around a top section. For the people who want a solution now, you have a couple options to how you can fix it.
1- Print with fewer walls and a higher infill. Your parts will usually come out nicer. I usually print around 50%infill with 3 tops, 2-3 bottoms, and 1 wall. Prints come out great and are plenty strong.
2- Use multiple profiles for different sections of the print. If you still want 3 walls you could print with multiple profiles to achieve nice filled top sections. Use the Cross section tool to determine where your tops are. Use the Stop printing function in the Other tab, enter in 3x layer the layer thickness below a top layer(i.e. If your top is at 10mm and your layer height is .15, you would enter in 9.55mm. Create a new profile with 1 wall and use the Start Printing box to start at the point where your last profile stopped(9.55mm). Also your 3 wall profile doesn't need a top or you will have 4 solid layers in a row. You can repeat this process if your object has multiple Top areas.
Can you post a picture of your top. It would help to diagnose it a little.
Also one other thing I adjust from stock settings that helps with caps is the "Outline Overlap" in the infill tab. I am usually print around 15-18%. The stock setting is 5 and it doesnt really push the infill into the perimeter as tight as I liked.
Are you using Kaink's 15-18% adjustment, or the 5% default, or ??? Other details on material, settings, etc? Nice print! My top surfaces are still just a tad rough -- I'm using 20% infill and 3 top layers.