There are some other elements which glitch around
All of these problems with misplaced and glitched elements started when I was trying to resize the original wizardform way back, which was - to my naive surprise - problematic in the past because there seems to be a internal limitation in Inno Setup source for some reason (if you want to make the installer surface bigger then default). Not sure but I think it was the Wizardform.Innerpage which was the real problem, that's why there exists a funny procedure GrowWizard to get rid of this problem.