Sorry for the delayed response.
From your setup to be honest quiet difficult to say what cause that issue.
The sync problem can happens where the incoming clock are not stable enough, or there’s a clocking issue on the network. Does the M32 mixer is the master on the network? Do you sync every device on the network to this source?
Could you please make a following test?:
Put the uTrack-X32 card to the M32 console (if this device is the master on the network) then start the recording there.
Check is the problem still happens or not. If does not happens in this case the slave device x32 does not get the proper clock somehow.