Just a guess, but it sounds like the orings are slightly worn. This can sometimes mean the bolt area is not sealing quite right, and therefore all sorts of issues could happen, including what you are describing.
Change out the orings and re-chrono.
Id leave the input pressure at a tick under 200. Definitely DO NOT go over 200.
Id put dwell on 35ish and BIP on 6 or more. Other settings - do as you wish.
One of the o-rings to check when velocity is low and won't go higher is the o-ring on the poppet. If air is bypassing it, the poppet never really opens properly. This can be more common in very cold conditions when the o-ring shrinks slightly.