“deleted by itselff” - so what happens, whats left behind in
a) Studio- Device (eg is it empty\none, your previous filament etc etc, is their a Bambo RFID spool in that slot?)
b) On the actual printer console, what does it read\say the AMS has in it?
c) if you manually change it on the printer console, in the AMS section - does it KEEP it on
c-i) the printer console screen?
c-ii)Bambu studio deice-ams selection ?
I am in an 24hr print, so I ccant test extruder presets myself, but I would consider logging a support ticket, provide bambu studio and printer logs etc, if you can repeatdily confirm this after a power cycle and \or even try re-pairing your printer to the account, I know some people have success with that step when their own custom filaments dont sync.