I've done some googling and while I found some threads with some stylesheet issues with saving none seemed to mention this bug.
I can't add any games to my Games I Own list. I turned the list into an unordered list (because ordered lists did warn me of a hard limit of 100 titles). I go to the stacks page, edit my "Games I Own" stack, add some of the games I've recently bought to the list, and the games do appear at the very bottom of the first page (page shows 100 tiles, list currently has 130+), but they won't be added to the list when I click "Save and finish".
I can't tell for how long this has been happening, but I've added 6 games in the last couple of days and none of them shows in the list. List is stuck at 139 titles no matter what I do.