My first visit here...hello!

We have a Series 1 NC, Boss 6, that is showing an odd problem. When a program beyond a certain length is loaded, a few characters in a few lines of code become changed. X becomes k, etc. The error repeats regularly when we reboot. We are able to load the program without problem, but the characters corrupt while the program is run. The machine will run correctly for 20 lines or so and then ignore a G2 code. When the program is downloaded, we see the changes.

Any ideas about fixing this?

We don't find the ROM chips available. They seem to be marked for specific locations on the board. We thought to move chips from the middle to the end of the memory, but are not certain about how to identify which one might be defective, consequences of interchanging... Are replacement control boards available for sale?

Thanks for any help,