Hello, it seems that because Forge's UniversalBucket doesn't extend ItemBucket, this check fails, resulting in turtles not being able to place liquids in packs that use the universal bucket.
I've also been having difficulty using place to fill buckets from in-world tanks but I'm not sure if universal buckets break that as the empty bucket just seems to be a regular vanilla bucket item. I may be wrong though, honestly not sure.

This looks like it might be an issue for modern versions of the mod as well.

• MC: 1.12.2
• CC: Tweaked: 1.89.2

I'm afraid Minecraft 1.12 is no longer supported, so this won't be fixed.