It seems that SpatialIO doesnt work in r5 (which i expected). I have learned that when trying to use the system and interact with a ready-made SpatialIO system, its non-responsive. It doesnt crash the game when you trigger redstone on the io port or anything. It just does nothing. However, when you try to save and exit to main menu, you crash and below is the error log.

• Error: https://pastebin.com/VJtFmkDZ
• Minecraft Version: 1.12
• AE2 Version: rv5 alpha 2
• Forge Version: 14.21.1.2443

This is most likely already fixed in #3018 and therefore should be fixed with the next release.

As discussed this is not fixed in that PR. We have to make a change or 2 in the code before it is fixed.
You can hotfix this right now in the config files by changing spatialio.storageProviderID to something else than -1. In 1.10 and previous versions this defaulted to -11.