This sounds kinda similar to https://mods.factorio.com/mod/simultaneous-research/discussion/6a1a42fb6216902acb5ebc92 , but not the same I think?

16798.429 Error MainLoop.cpp:1488: Exception at tick 119702244: The mod Parallel Research (0.8.3) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event simultaneous-research::on_lua_shortcut (ID 43)
simultaneous-research/scripts/lab_utils.lua:251: attempt to index local 'prototype' (a nil value)
stack traceback:
simultaneous-research/scripts/lab_utils.lua:251: in function 'undigitize_packs'
simultaneous-research/scripts/lab_utils.lua:275: in function 'undigitize_inventory'
simultaneous-research/scripts/events.lua:108: in function 'toggle_mod'
simultaneous-research/scripts/events.lua:84: in function <simultaneous-research/scripts/events.lua:82>

Have you by any chance disabled a mod that added new science packs to the game? That would explain the error.

If no, then please upload your save somewhere.

I upgraded my save from 2.0 to 2.1, in the process I did disable Pelagos (which does add a science pack, I plan to just add it back when it updates and redo the planet later), it loaded up fine from that though. This error only happened much later when I tried pressing the toggle Parallel Research shortcut button. It still happens whenever I press that shortcut button.
Is google drive fine for sharing my save?

No need for the save, that's enough info.

Should be fixed.

The mod Parallel Research (0.8.4) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event simultaneous-research::on_configuration_changed
simultaneous-research/scripts/tracking_utils.lua:109: attempt to index a nil value
stack traceback:
simultaneous-research/scripts/tracking_utils.lua:109: in function 'refresh_lab'
simultaneous-research/scripts/tracking_utils.lua:97: in function 'add_lab'
simultaneous-research/scripts/tracking_utils.lua:10: in function 'initialize_labs'
simultaneous-research/scripts/tracking_utils.lua:30: in function 'reinitialize_labs'
simultaneous-research/scripts/events.lua:68: in function <simultaneous-research/scripts/events.lua:67>

I just got this today, was working fine last night, updated a few mods today and blam.. no worky..

Mods as of today:
P.U.M.P.
PlanetsLib
simultaneous research
upcycler planner
panglia planet
energy category
frozen food

Gonna need a save for that one. Please upload it to any public hosting.

https://filebin.net/m94ho7835a63gea3

Okay, you are saying you use seven mods, but the save you uploaded uses like a hundred, some of which aren't on the mod portal. The save doesn't load due to Even Distribution mod crashing, possibly due to missing mods. Check if it's a correct save.

LOL Sorry, I merely meant those were the only mods that updated themselves when this error occurred, apologies for the confusion.
The save loads because I disabled Even Distribution.

Okay, should be fixed.