Navico corus windset problem
 

On my boat I have Navico Corus instruments. (pilot tp300, multi c400m,
datacentre c700dc,nmea 600)

The problem is that my windset gives suddenly an inverted winddirection.
After replacing the set with my spare masttopunit the problem was the same.
I think it must be possible to invert de winddirection. Does anyone know how
I can do it?
Thanks,
Peter