So I'm aware this has been brought up already But my issue is caused by the creation of a wither boss... not sure how the 2 are connected but everytime someone tries to spawn one the server crashes and gives the crash.

Sponge thread:
https://forums.spongepowered.org/t/crash-on-wither-spawn/18603

Crash:
https://pastebin.com/WH39GXz9

Man, I don't know... perhaps the people at Sponge could be a little more specific in what I'm apparently doing wrong to break their API all the time. I just can't understand how the issue is on NC's end when it runs fine without Sponge.

Have you tried contacting them about it?

I will do :)

Cool! Love your mod and really dont want to have to remove it from my modpack :(

not sure what is happening exactly but it's calling the below recursively until the JVM reaches a StackOverflow
https://github.com/turbodiesel4598/NuclearCraft/blob/1.10.2/src/main/java/nc/tile/NCTile.java#L58

Should be fixed in the latest version 2.2 :)