Last year I had some issues on our own new boat with the NMEA 2000 network. Some devices, in particular the Airmar sensors, would suddenly drop off the bus as if they were no longer there. After about ten minutes or so they would magically reappear. Most often I would not be that patient and cycle the network power; this helped all the time, but was very annoying.
The problem happened a few times a day for the DST-200 depth/speed sensor and about once a day for the PB-200 multifunction sensor. I thought it was interesting that only the two Airmar devices had this issue whereas the 10+ Simrad/Lowrance/Mastervolt/Actisense devices on that same network had no such issues.
I can now report after 2 months of testing that this can be fixed by loading new firmware into the Airmar sensors. This can be done by downloading the Airmar Weathercaster software and then applying the firmware update through that. Note that this is the approved manner of doing this, even if you do not own a PB200 but only a depth/speed/temperature (DST800) or depth/temperature (DT800) sensor. I upgraded the DST800 to DST200_a1_1022 and the PB200 to PB200_a1_1611_a2_1611 after which the problems have been fixed. According to my friendly Simrad engineer, Airmar actually repaired the issue in software release 1021.
Link to the Airmar download page