Hi Andreas,
its totally normal that with a non integer scaling factor, that calculated pixel positions may will collapse on the same physical position.
Example:
if the non-scaled coordinates are 2 and 3, they will transformed to 2,5 and 3,75 (with scaling 1,25) and will be part-wise mixed on the same physical pixel 3.
The problem described in this topic is that there is a graphic function doesn’t work this way: the int version of fillRect. If you use this function, you should replace it with the float version, so you can be sure it will look nearly the same on both platforms (if they use the same scaling)