WP7609 AT!MUXMODE error

Sometimes, during modem startup, I get an error
AT!MUXMODE?
ERROR
AT!MUXMODE?
ERROR
(ERROR causes a command retry)

Other times, it works as expected
AT!MUXMODE?
!MUXMODE: 1

I change nothing - it seems to be a random behaviour of the modem.
Software version = SWI9X07Y_02.25.02.01 000000 jenkins 2019/01/30 08:13:05
Any suggestions please?