After quite some time of this issue I finally resolved the checksum issue on this unit.
On boot up the unit would give an error. What I found was a battery on the CPU board was dead, Not having a solder in coin cell battery on hand I simply mounted a coin cell hold to the rear of the CPU board. Was not enough room to mount on component side.
The battery solved the boot up problem.
https://www.youtube.com/watch?v=S7U9EGVQwPM