I've experienced a weird crash triggered by jeiintegration_1.16.5-7.0.1.15 whenever I tried looking over a particular mod's in creative tab in creative mod.
I've already explained the situation and shown the crash logs to the mod author of the mod in question (slashblade for 1.16.5)
and so far they can't there isn't anything they can do for fixing the mod conflict/crash under the very exact conditions that are trigger the crashing of Minecraft only by while jeiintegration_1.16.5-7.0.1.15 active in the same mod pack as the slashblade mod.

So I'll paste the paste bin link of my crashlogs now and hope that there might possibly be some way to solve the mod conflict from jei integration's end.

https://pastebin.pl/view/a0b5d654

Lastly I would like to note that I'm using the Lastest version of the forge - Version "1.16.5-forge-36.1.4" during the crash logs if that information helps any, and that the same crash issue occurs persistently in all versions from the current recommended build of "1.16.5-forge-36.1.0" and up.

I haven't been able to confirm if this occurs in earlier forge 1.16.5+ builds as mods within my mod pack require that I use no older then "1.16.5-forge-36.1.0"
I'm hoping all this information was helpful.

Honestly not sure here. I can't see anything that would cause an issue. All I'm doing is getting the NBT and appending it to the tooltip. So, the only thing that comes to mind is there's too much NBT data? But I find that an unlikely cause too.

All I can suggest is using the latest version and see if that fixes it. If not, then just try avoiding this scenario or disable that tooltip. It doesn't have many player-applications its more a debugging tool.