I was playing on my world when i opened a millénaire locked chest and the game crashed (with vanilla fix) crash report: https://paste.dimdev.org/zanoveyomo.mccrash . Forgot to mention my inventoy becomes invisible until either i use the slot and the item reappears or i rejoin the world.

UPDATE: There's a chance it has to do with aromabackup as the glitch occurred again right after the backup was done. Not sure where better portals fits in with this but meh. maybe opening the chest just updates something?

Sounds somewhat related to #310.

What I concluded over there, applies here as well:

I was going to check how the Millenaire mod implements its chests but it turns out that even though they have a Source link on their CurseForge page, they don't actually provide any source code for their mod. So, please report this issue to them and let them deal with it cause I can't.

If you do report it on their issue tracker, feel free to link to it here, so that anyone also encountering the issue can check on its status.