Got told this by a friend, will validate later:
Any time he put on the SGs, the game would crash, and upon load, the SGs would be deleted. He had two, one he shift-clicked into the slot, and the other the right clicked w/ in-hotbar.
Will get crash logs, mod list, and testings done myself eventually, but that's the issue.
OpenBlocks is the current version, as far as I remember.

Issue is really old now, closing. I will create a new one if it ever comes up again.

Any updates?

Yes, I forgot to post an update. Silly Therm.

We took a quick look with a new superflat world and we were not able to replicate the crash to post a log. He was clearly expecting it to crash as soon as he put them on, but was impressed with the experience when it didn't.

After a while, I'm thinking it might be triggered by a combination of different graphics settings in MC. I'm putting it on our to-do list when we test again.

Sonic glasses sometimes crash on specific graphic cards. No idea why and can't ever reproduce.

If this is the case, I suggest updating drivers.

Bah, humbug....hate updating hardware. I'll get the log later to make sure that's the issue.