Apparently this behavior was introduced with 4.1, but I don’t know where or why.
A fix would be to discard the pitch of the control rotation using break rot followed by make rot.
I’m running into this also but in the first person blueprint. I thought i may have been onto something by breaking the vector and discarding the Z info but this did not work. Nor did setting the Z to anything else.
I just fixed the templates for 4.2 on Friday, sorry about that. Now in FP I just use the pawn forwards/right vector instead of the control rotation. This actually simplifies things as well, should have done it like that to start with!