Position report data conflict

[Karanga]

I have mentioned this in previous posts, but now it is pitching me off!
I am running OpenCPN 5 (build 1448) on a Windows 10 laptop.
Position data is provided by an aerial puck through a USB serial adapter.
AIS is provided by Digital Yacht AIT3000 nmea via a USB serial adapter.

The problem is that these 2 fight with each other over their position reporting. It doesn't seem to matter which I select as priority 1 or priority 2.

I have instructed O5 to ignore the GPS data from the AIS. I have also turned off the GPS data from the AIS.

With the AIS com port disabled, my position is a smooth, consistent line. As soon as I enable the AIS port (with all GPS data turned off, plus sentences ignored) my position report drops out, SOG and HDG disappears. Sometimes VMG continues, but not always.

My recent discussion with the AIS guys suggested that the AIS position is coming from their ownship data (!AVDO). I don't think it is possible to ignore this info. But is it correct for O5 to be trying to update nav info based on this info?? Especially if that has been set as priority 1 against the aerial puck set as priority 2?

[Hakan]

Karanga..
Normally your own AIVDO should give no problem but if you receive a strange one you can test o filter it out, like my shot: