Just updated to 1.17 and found that the 1.16 version 1.1.3 was marked to work with 1.17 and it loaded up fine. However when I tried to hold a shulker box with items in the game fully crashed, I have tested this on the server I was on and on a single-player world. I happens with any shulker box with items in. I could have the boxes in my inventory just not in my hand. I have attached a crash report.
crash-2021-06-09_16.20.07-client.txt

Can confirm. This has happened to me (went to Issues tab just to report this issue and someone already has).

Just incase if one Crash Report/Log isnt enough for whatever reason: https://hastebin.com/ikiyuxades.yaml

I'll update the mod to 1.17 soonish (iirc it was marked compatible with 1.17 because it worked on the first snapshots and curseforge didn't have the '1.17 Snapshots' option)

(Hopefully) fixed in 1.2.0, looks like recompiling was enough