Did you file a bug report? We are experiencing the exact same issue.

I am also noticing the issue is specifically with DTMF tone duration. The PBX thinks the device is sending multiple DTMF tones instead of a single tone. So taking your example of 3121 we are seeing 33311222111. DTMF tones have specifications for duration and space (silence) in milliseconds so something must have been introduced that caused these tones to be generated with incorrect durations or the generation is being interrupted just long enough to introduce some silence for it to appear as multiple tones to the receiving device. If you enter a comma in between every single tone, like 3,1,2,1 it works correctly but this significantly increase the dial time. This could affect all "Tap to join" meeting invitations from Zoom, Google Meet, etc., that provide a single phone number and access code to join a meeting.