Yeah, I've had exactly the same problem!
With me, it wasn't the Beatstep, but the Microbrute's Gate that wasn't working with Pittsburgh Modular Modules.
I could add that the Mbrutes' CV is not exactly 100% in tune over more than 1 octave too here,
but I'd really be going off topic big time
It seems, I'm not alone here in encountering this problem a lot with Arturia's 'curious' CV Gate outputs after reading
a number of forums.
Anyway, whinging aside, my solution was to run the Gate through a buffered multiple.
Since then, it hasn't been an issue.
I have to add though, these posts have put me off buying a Beatstep, which is a shame really
since, on paper it looks great for the price.