@dankcushions Perfect. Thanks!

My setup is complicated by my son having a specific ROM set and my using a share to connect to those. It sounds like I might be better off just using MAME2003 core and finding the ROMS for those versions and keeping them all on the SD card of my Pi 4.

@mitu lol nah i remove it before posting lol

Yep, same problem here. Just updated mupen64plus from binaries, no changes. Crashes everyone when trying to load a state... Saving states works though, can see the files in the folder being created, also they have the current timestamp.
Using mupen64plus-gles2n64 btw.
€dit: Loading the savegame seems to work when i'm editing /opt/retropie/configs/all/autoconf.cfg , changing
mupen64plus_audio = "1"
to
mupen64plus_audio = "0"
This though leads to no sound anymore, loading the savegame with the same key combination though works then...

@herb_fargus Well I mainly use Final Burn Alpha for all of my arcade roms, save for NBA JAM. I need to use MAME for that.

Apologies, I thought I'd performed a fix that I actually didn't end up performing. I set mupen64plus_audio=0 at /opt/retropie/configs/all/autoconf.cfg, and load state now works. Received the fix from here: https://retropie.org.uk/forum/topic/3897/solved-pi3-retropie-4-0-2-some-n64-games-crash-when-trying-to-load-state-using-any-of-the-mupen64plus-video-plugins/5

Works also on my end. Thank you!