Disclaimer: the following is just thinking out loud:
The wrinkle seems to be the [W] along with record enable & recording. If there were a bug, I'd guess it to be related to this wrinkle.
And it seems clear that the pitch bend events or envelopes were not
recorded to other tracks, but at some point got
echoed to the synths on those tracks, leaving behind some non-zero final values in the synths which could then be cleared by various means of sending pitch bend of '0'. (This is assuming those other tracks did not vary in pitch bend amount during any playback after the offending incident but operated as if they had been left with a single pitch bend offset.) If that's the case, did those synths
not sound like they had shifted pitch during the possibly offending recording phase? If they did sound wrong then, it would be evidence of events weirdly leaking over to other tracks during [W] with recording. If they did
not sound wrong then, the events must have been sent when the transport and all sound output was stopped, which would be even weirder.
Another weird thing is that those other tracks didn't receive a final '0' which would have been the most likely final event, given that the pitch wheel was most probably returned to 0 before [W] was cleared and recording was stopped.