[TenTec] Omni VI plus

[Maurie]

I wonder if anyone can assist with this query.
My Omni VI plus seems to have an issue in that the frequency readout does not match the CW transmit frequency. The difference always seems to be the CW offset which is 700Hz.
This occurs on 17, 12 and 10mx. All other bands are perfect.
For example .. on 17mx ...at exactly  18.100Mhz on the display  ..if I send CW ..the tx frequency is actually 18.100.7On 10mx..if I send at a readout of 28.050 the transmit frequency is actually below at 28.049.3
All other bands, do not do this, and are perfectly in sync, meaning it transmits exactly at the frequency that the dial- readout indicates.

For some days it was also affecting 15mx, but then it stopped as suddenly as it began, and 15mx is now back to normal.
Suggestions?
MaurieVK3CWB