For everyone with 139/140 conjurations, or 74/75 traits. Both are avoidable with foresight, and I got very lucky in both instances personally, but sadly nothing you can do in either case until a patch if you're affected.
Both have active bug reports on the official Hogwarts Legacy bug page.
139/140 Conjurations - This glitch occurs because the butterfly chest tied to "Follow the Butterflies" is
missable (verified on Reddit). If you trigger the butterflies but don't complete the quest and complete another of the 14 butterfly chests elsewhere, you'll be prompted to go back to the quest giver despite not completing the "intended" butterfly chest. DO NOT HAND THIS QUEST IN YET. If you complete it, the "intended" butterflies for that side quest become permanently unobtainable! If you've made this mistake but HAVEN'T turned in the quest yet, you should still be able to find the "intended" butterflies for that side quest, which from memory is by the forbidden forest. I was lucky, and happened to do this side quest as intended hours before I mopped up the remaining 14.
74/75 Traits - This glitch occurs when players just aren't credited with a trait when completing a bandit camp. I strongly recommend that when you loot bandit camp chests and/or turn in challenges, you triple check your collections page increases +1 for the collectible type. Again, nothing you can do if you've collected them all and are 1 short, sadly.
It's also worth noting that virtually everyone will get "stuck" at 33/34 field pages for Hogwarts > The Bell Tower. This shouldn't matter, as the one that is bugged is an Accio page by the greenhouse/gardens. Thankfully, it's the one collectible type where you don't need to collect every one (Revelio you do; field pages you don't).
Quelle:
https://www.trueachievements.com/viewcomment.aspx?commentid=1710720#sc1710720