What's the issue you encountered?

Hanging signs cause crashes on both servers and singleplayer worlds, on the newest version of everything. Unlikely to be a mod compatibility issue (I checked by disabling everything else and it kept happening)
I've checked existing and resolved issues and found one such as this that was marked as resolved, but the resolution was to update to the newest version, but it's not applicable here
Thank you very much in advance!

How can the issue be reproduced?

Enter a world
Give yourself a BoP hanging sign of any type
Place it down

Logs

https://gist.github.com/Arpel21/ee598a6a96e61871e538287de09a3eea

Mod Version

21.1.0.4

Additional information

No response

Same problem here!
Is this similar to #2253 ?
But this PR dosen't update HangingSignBlockEntityBOP