All details can be found in this crash report. Not entirely sure if this is indium or sodium, figured I'd fire it here first.

In more recent versions (Sodium 0.3.x and newer) this should be fixed; see also CaffeineMC/sodium#942

Quick update - I believe I've isolated this issue down to specifically being caused by Crafting CPUs, specifically being in proximity to them.

Thought I'd also mention that the logs keep getting spammed with errors like:

[17:47:58] [main/ERROR]: ########## GL ERROR ##########
[17:47:58] [main/ERROR]: @ Pre render
[17:47:58] [main/ERROR]: 65539: Invalid key -1
[17:47:58] [main/ERROR]: ########## GL ERROR ##########
[17:47:58] [main/ERROR]: @ Pre render
[17:47:58] [main/ERROR]: 65539: Invalid key 0

Figured this might be tangentially related to this issue.

A third issue better related to this one, with a bit more of a severity:
crash.txt
This report seems to be a bit more detailed than the last one so I hope it helps

User logs on, terrain renders for a bit, they see this before crashing with the report above:

where what I see is this:

That screenshot looks like a registry desync issue, where the mods aren't matching on the server and client. Does it work without Sodium and Indium? Ah, just saw the other issue! I'll look into this when I have time, probably sometime next week.

I haven't managed to replicate this myself, and the world file was removed before I had the chance to download it. Could you try the 1.16.x/experiments/renderattachmentcme branch of Indium - it has some extra debugging code to attempt to see what exactly causes this issue. Please also test without Indium, as I don't see why this wouldn't also happen with Indigo.

the world file was removed before I had the chance to download it

ahh yeah sorry about that, google drive only gives 15 gigs of storage and the world save was taking over a third of that. I mistakenly assumed you saved it, my bad.

I'm also on a bit of a break right now and away from my main PC. I'll be back at it in a couple weeks. I'll see if I can have a friend of mine test in the mean time.

Hmm, what mods are you using that require Indium? It looks like a mod is modifying the block entity list during getRenderAttachmentData, but I can't seem to find any mods that do that...

AE2 textures don't render properly with sodium unless indium is installed - on installing indium this seemed to fix the issue, but created this infrequent crash. See CaffeineMC/sodium#538

Does this crash occur when loading the world, or after you'd placed/broken a specific block? If the latter, which blocks were you using?

This crash occurs when walking around the world, generally looking in a specific direction. We load in perfectly fine, and can play for hours on end, it's just when we go into a specific place with a lot of AE2 blocks/block entities, and look in their direction. Physical line of sight is not required.

I will comment here that this crash only started once we had auto crafting set up at my base, maybe it could be one of the crafting storage blocks?

Hmm... could you send me the world that you managed to produce this bug with? No worries if you don't want to, I can hook up some debugging code to Indium and let you test that, but it'd certainly make things quicker to work on the world directly.

Sure. It's a 5.6 gig (when compressed) multiplayer server, so grab a cup of coffee or something, this will probably take a while to download. Have the world and the modpack
The place where it happens is the machine room of our starter base, at +1632 8 -2047. If you run around there, looking around it should eventually crash. A lot of my friends crash by coming in from the entrance teleport pad and looking west.

Honestly, you might want to just give me a build with the debug stuff builtin, I think it would be easier for the both of us :P