Maybe I've found the source of the bug. Seems to be related to the "parameters" section. For every product system added, thath window become larger, after the 6th (on my screen) it is so large that the selection voices inside the pop-up windows become unusable.
So, I think that in this version the pop-up window is enlarging along with the containning window (to me seems it is enlarging with a 2x factor) making the selection impossible, in relations to the number of product systems added to the comparison.