Aha. I send all MIDI data into my racks, but my racks have song-related rack states selected, which internally have a number of input routes, each of which allows only one type of data - note, sustain, mod, aftertouch etc, which I then enable/disable on a rack state basis. Same result, different approach, I think.
The “Block until complete” suggestion was any for bindings that are triggered on song load, or to actually select songs (e.g. in your background rack), to ensure consistent initialisation, rather than for the problematic bindings dealing with routing your controllers. But still, it was a bit of a shot in the dark, based on the observation that your songs behave differently depending on how they’re selected - the suspicion that something in the way your song is selected affects subsequent behaviour.
You don’t have jump prevention enabled on the bindings do you? I’ve had some unusual jump prevention problems in the past that happen when different controllers are mapped to something with jump prevention enabled.
Neil