Doesn't the mother 32 have weird CV tracking or something like that? I googled "Moog mother 32 cv in issue" and there is quite a few people with mother 32 cv problems. It's why Erica Synths released that Pico MScale module, right? Does the Beatstep have different voltage settings for the CV out? Perhaps it's set to work with the mother 32 but not, uh, "normal" V/Oct?
I don't own any of that so I'm just guessing.