[CA] [CA11] E90w/e120w not following saved routes properly

[Dustdevil]

Hi Folks,
Sit back, grab a cup of something hot and dig into this one.
I'm working on a system right now with multiple Raymarine networks going and have a strange problem to report. Hopefully it's been seen before and is a simple fix.

The boat will go to a waypoint just fine, but will not follow a route properly. It follows a parallel course about .3km to the east. Heading of the icon changes slightly at times while following.

The yacht in question has 2 MFD's, an e120w at the nav and an e90w at the helm. They are networked together via Seatalk hs thru a Sirius weather module with multiple ports. The radar networks here as well, and it's a rd418hd.

The boat also has a Seatalk ng network that the raystar 130 gps, raymarine AIS, and Evolution A/P connects to, which is running an ACU-400, R70 control head and EV-2 heading sensor.

The boat runs standard Seatalk with ST-60 wind, speed and depth. It had previously had an ancient ST7000 autopilot networked in that was replaced to solve the current problem, with no joy.

Commissioning of the new autopilot went very smoothly with little deviation and excellent steering characteristic with the exception of the route following.

Thoughts?