Error Code >OT

Working on a plasma thawer. Thermogenesis MT204 Initial call came that unit was not heating. Ohmd out element and it was fine (10.6 ohm) Did replace the temp probe Keypad data entry is hit or miss. Will not always accept codes 100 or 200 for temperature. The other gremlin is that the unit will sometimes start a cycle, fill the plasma bath, but then will shut down with the error code >OT Call to tech support and they have never seen or heard of such an error. Any ideas?