Me neither, I have never used Ableton Live. Maybe another user will help you.
Anyway, let's summarise:
-- everything is OK when AT5 is loaded into Live, no preset switching,
-- when using AT5 standalone program, the preset switches back to preset 1 frequently.
That sounds like the hardware is sending Program Change messages to the software (Live may be discarding them and not passing them onto the AT5 plug-in). That is why I suggested recording or looking at the MIDI coming from the hardware. Also, review 10.3.1 in the AT5 User manual to see if that gives any clues.
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