Lots of mods did not implement the new forge capability system and only extends/impelments IInventory.

Like iron chest, ender storage, dimensional storage and probably a lot other mods.

It turns out this line is incompatible with those mods because they will simply fail on this.
https://github.com/Creators-of-Create/Create/blob/mc1.15/dev/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/MountedStorage.java#L125-L127

I am not sure whether this is a problem or not since the forge also add capability to the vanilla chest.
So this is probably mandatory on all mod entities that want to make itself behaves like a chest and those mod did not do it correctly?

See also: issue opened on iron chest's side

Edited: it turns out ender storage, dimstorage do implemented capability, but it still not works with contraptions, why?

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

This issue has been closed since it has been inactive for 3 weeks since it was marked as stale.