Many thanks for your replies. Makes it much more clear to me. Still
though it's a bit strange phenomenon to me: I have understanding for
the phenomenon (my code isn't 100% bug-free neither), but then a third
party piece of software (or yourself) has to take care of this... ?

I just used VBA Cleaner for the first time after a month working full
time on a project. For as far I know I hadn't any problems compiling.
(It was just bad luck for me, because cleaning didn't solve my spooky
problem with the ControlSources. But that's maybe another thread worth
it..)
I make sure to clean the files before delivery. Thanks again.

Bart