Infill partially starts too early

[Richie76]

Version

1.31.6-prusa3d-win64

Operating system type + version

Win 10 Pro 64bit (fully patched)

Behavior

While printing a number plate for a child´s car (bobby car) I ran into the following issue:
The infill started right after the 1 solid layer in 2 regions of the print and in other parts after layer 3 (settings were 3 bottom and top solid layers).
The behavior is visible in the preview and the layers view of the model:
Here are 4 screenshots of the zoomed in part (it happend on another part too - but this is better visible):
In the lower right corner is the layer (and i add them in increasing order too):

STL/Config (.ZIP) where problem occurs

The stl file was printed with the letters facing the printbed (there will be different coloured inserts to be put in).
config.zip

[bubnikv]

I believe this is a duplicate to
#60
#79

and it has been fixed already. At least I don't see the problem with the master version. Please stay tuned for the next release.