Gum worm parts tend to stuck somewhere resulting in long ropes of gum across the biome.
Gumworms also always come out to the surface exactly when they are inside normal caves where there is no empty space. At the end of the video all worms stuck inside water but I guess this is normal. Tested it without other mods.

Same issue, running the 2.0.1 version on NeoForge 47.1.106 with the only other mod being the dependency, Citadel.