Reel to Reel tape question

We don't seem to have a tape forum here, but analog is analog, so I'll try it here: Does anyone know why it is that my fully refurbished Revox A77 makes my four-track, 7.5 ips tapes sound better after I flip them over? Meaning, on side ll? There is a greater clarity, more dynamics - just a better sound after it plays through side l, and I flip it over. I thought that it might be the tape deck warming up, and so it sounds better because it has been on longer for side ll. I then turned it on, let it sit for an hour, and then played it, with the same result.

Is it a matter of alignment, perhaps? Any other thoughts?

Thanks,

David