I have an FMX project with a lot of forms that have BorderStyle := bsNone
set during design time, and every time I open one of these forms the IDE will increase its height by 23 pixels. I'm currently using XE5 but I had the same issue in XE2 which I have been using before.
The issue can be reproduced with a vanilla desktop project with one FMX form, but does not appear using VCL.