Modpack version
1.78

Can this issue be reproduced?
Yes

Issue
I noted the same issue as noted in a previous thread, but the seals only seemed to disappear when placed on a tile entity (plant, farmland, etc) but not when placed on a static block. So far this has been stable, so I'm not sure how to resolve storing items with golems without placing the seal on a tile entity. I will have to do some testing myself.

Originally posted by @pauldwrona in #924 (comment)

Thanks for reposting with more details - I highly doubt this will be fixed though to be honest, Thaumcraft seems for the most part abandoned.

I've decided not to take this issue any further, as most modders no longer work on Minecraft 1.12, and development of Enigmatica is focused on Minecraft 1.15+ - I hope that's understandable :)
Thank you for helping to make E2E polished by reporting, I hope to see you in E5+!