[Yaesu] FT990 Issues

[Robert Pack, NX5M]

A friend of mine is having trouble with his 990.
Seems to be a frequency display problem vs the actual frequency.
We met on 28505.00 a while ago but he said that is radio was showing 28504.5.
He also told me that on cw, it was doing the same thing so we checked on a dx station in the CQWW contest that was on 28027.1.  His display showed 28026.6.
Also during our ssb conversation I noticed that his frequency changed a bit.

Any clues what could be causing this?
I will forward any valuable information to him.

Thanks.