MTS2000 and RMN5023B Commander Mic issue

[MotoFAN]

Hi all!

I use RMN5023B Commander Mic with MTS2000 Model III, firmware ver. 05.40.

Basically it works fine (excluding Volume buttons, of course), but sometimes radio spontaneous makes two sounds ("beep", few seconds pause and "bup") and radio "jumps" to other zone and channel - accordingly to the Zone selector (Toggle Switch in my case) and Channel selector (Rotary knob on radio) positions :(

For e.g.: I have chosen Zone # 4 (via radio menu) and Channel # 3 (also via radio menu). After few minutes...hours of operation or reception two sounds appears (beep/bup) and I see that radio is already on Zone # 1 and Channel # 1 (accordingly to the Zone/Ch selectors positions on radio).

Mic is new. Radio also has no any issues. ACC connector contacts are clean, mic connector pins also ok, and connector holds well on radio.

Any ideas?

P.S.
I know that this mic not officially approved for MTS2000, but thus it is not prohibited (unlike is MT2000, JT1000, MTX8000 and MTX9000 which are obviously forbidden in mic's user guide) and major features practically works fine.

[MotoFAN]

F/W upgrade can solve situation?