... brings you to the main album. Hm, i would expect it to go back to where i came from which means from the images of the subalbums. Should I put it to GitHub? Is it bug or is it not worth mentioning it ;-)

Breadcrumb example:
Edit Album: mainalbum/sub1/sub2/sub3

Do you mean that when you are on a single-image-edit-page of sub3 you want sub3 to be an active link?

I see that as well - rarely use the "back" button somehow – and for sure it is a bug ;-) So yes. please a ticket.