Any Bucket or Minecart made with any Vanilla/IC2/GregTech-Metals (except Iron ofcourse) is automatically removed to prevent exploits with reverse Macerating/AlloyFurnaceSmelting Buckets into Iron.
Well actually, the buckets they make aren't able to be put in the Alloy Furnace(as far as i know) or be macerated into iron, since the tin recipe in the mod literally makes a Tin bucket, not just the normal one, same deal with copper. the only machine recipes they have is being able to be filled and used. I am glad that you made your mod auto-disable that recipe though, since the exploit kinda ruins the fun.