[CA] [CA11] Axiom Pro speed jumps erratically

[Chief]

Chuck,
Changing the filter from medium to high has no effect at all, not that I can observe. What else can be checked?
One of the main issues I have when this is occurs (always above 14.8 Knts) when the autopilot is engaged and I’m trying to judge time to a waypoint. The time try’s to recalculate with changes in speed and the display becomes at times, difficult to read or unusable. Plus I have what amounts to flashing numbers on my instrument display which is frankly, kind of annoying.
I don’t understand why at 14.5 knots, it’s rock steady and at 14.9 it is suddenly Varies so much. I have never had any other Raymarine product or any other GPS do this. I definitely have a hard time accepting it as typical.
If I were to change the antenna selected would you expect the exact same issue at the same speed or would expect different antennas mounted in different locations to product different results? If I can duplicate the same issue with all three antennas would that help identify the cause?

Thanks,
John