This is a YOU issue as ive just tested this on a vanilla client and they def drop magma cream. So its either a mod issue or datapack issue or a server issue.
ed to fix tell next time bug hits had to whipe the hhd of all data reformat thin reinstall minecraft on to it stell dont know if it will bug agin but it may agin
Can confirm this. Having random stuff in the game is fine for some things but not things like this. It makes a lot of stuff especially on a technical level very unpredictable and unreliable and no one likes to deal with randomness when working on a project. This doesn’t affect just iron farms but a lot of other stuff as well. Ur now basically rolling dice whenever u try to do anything with the mobs that have this.