I had some users who reported a "visual" problem which looks identical to your problem. It turned out they were all using a customized ROM based upon MUI. It happened also with other apps which were NOT written in B4A.
I didn't look into to it further. :sign0013:
I don't see any problem:
I see a subtle difference, your button looks "plain" mine has a beveled effect, maybe a "theme" is the culprit? but, I can't see any settings or options for themes on this tab.
EDIT: It seems it might have something to do with "Styles", according to what I've read so far.