I had the same type of problem , to make matters worse mine was
intermittent. Even sent it back, they found no fault. After some head
scratching, I figured out yhat it must be power supply, it was the little
take apart "bayonet" connectors that ICOM puts in the two power wires (black
and red) that are a couple of inches from the radio. I removed these and
hard spliced the wires and no problems since. I would try that before
sending it back.

--
Ron White
My boatbuilding website is:
www.concentric.net/~knotreel