From what it sounds like, I THINK the problem is with your reader. You said while screwing the Hatty base in, the reader intermittently read ohms. That tells me that the reader center pin is spring loaded but you aren't getting a good connection.
If you compare the total length of threaded part sticking out the bottom of the baby beast tank, to the threaded part on the Hatty, one is probably longer than the other.
If you compare the total length of threaded part sticking out the bottom of the baby beast tank, to the threaded part on the Hatty, one is probably longer than the other.