OK, that’s really weird - you’ve come across a bug in PsychoPy itself that must be new and definitely shouldn’t be happening.
Hi Todd, @TParsons this might be one for you. Builder (v 2021.1.0) generates this code when checking if a stimulus contains a mouse click:
for obj in [[image, image1]]:
if obj.contains(mouse):
i.e. the stimuli to be checked are nested within a list within a list, so obj.contains() will always fail when iterating over the elements of the outer list, as it only sees it containing one entry, which is a list rather than a stimulus. Seems odd that no other users have been hit by this though, as it should be a show-stopper for many (unless I’ve missed it)?