As a reference point, I installed FM Go 12 on my iPad 2. I also upgraded FM Go 1.2.4 to FM Go 11.0.1. The buttons on my .fp7 files using FM Go 11.0.1 exhibit the same response as they did with FM Go 1.2.4.
If you haven't already done so, try your .fp7 files with FM Go 11.0.1 and let us know whether this helps or not.
I rebooted the iPhone, that fixed problem. Upgraded to Go 11.0.1, thanks, all behaving properly.
One issue I've discovered is that if the button is too small, Go has a bit of a problem deciding whether you meant to press the button or the background. I try to use buttons about 45-50 pixels square or bigger to avoid this. The bigger button never leaves any doubt as to what my intent was.
Try different sized buttons and see what works for you.