After a second upload of my world, it is now working. I'm trying to reset my other two world slots as well. I'm not expecting success.
I spoke too soon. The upload works now, but it didn't upload the correct world, somehow. This isn't my world, or I was spawned no where near my original spawn with a completely different character.
It looks like I managed to get my world uploaded, FINALLY. I had to:
Export my world
Uninstall Minecraft entirely
Reinstall
Import my world
Replace world
The other functions still do not work.
I guess I spoke too soon yet again. Now it seems like the reset works perfectly fine. :eyeroll:
Feel free to close this out unless you want to see if it's possible to post mortem this weird issue.