Another thing to consider is the shorts. For example, if they are old, is the chamois wearing out? Or is it bunching up or causing chafing for another reason? Or are the shorts too big?
How can you tell if a chamois is wearing out? Shorts #1 might be too big but I think shorts #2 are ok. I do have a third pair which are a liner and they are definitely tighter than 1 and 2 Perhaps I will try shorts #3 next time out and see if there is a difference.