AIS and radar targets are out of sync

[lvnmdrm]

Hello,

I have AIS650 and RD418D connected to my c90 MFD via STng.

My AIS ship display icon is off by several degrees, more or less depending on COG.

It is quite disconcerting to watch my ship moving sideways to COG.

More disconcerting is the overlay of radar.

Distance from a target, whether AIS target or land mass, seems to be an issue.

The further away, the more the overlay display is off.

A land mass target may be off by an inch or two, many degrees from COG, compared to the underlying chart.

An AIS ship target, similarly, will be off.

Stated another way, I will see two targets of the same vessel, one radar, one AIS, separated by some distance on my MFD until we have approached each other.

Similarly, I see two targets of the same land mass, one radar, one charted, separated by some distance on my MFD until I am closer to the land mass.

What might be causing this to happen and what is the solution to fix it?

Unfortunately, after reviewing the screen shots taken with the radar overlaying a chart, it appears the radar targets were not captured.

Thank you,

Dan