Brother HS-50A - I/O Timeover 4 error

Guys, just hoping someone might have some insights on this problem.

The machine runs fine, then all of a sudden out of the blue I get this:
5037 - I/O TIMEOVER 4 error.

Power off, Power on, start machining, and it goes just fine again for .. well sometimes the rest of the night, other times for an hour, or perhaps a few minutes.

Power cycle again, restart and goes fine again ...

Rinse and repeat.

According to the Maintenance Manual, the error means:
Framing error occurred during communication between DC PCB and NC unit.
1: External noise
2: Faulty DC PCB or cable connection.

Now, I have done the obvious unplug, reconnect, reseat etc of cables and boards.
I also have no "noisy" machines anywhere, let alone near the EDM.

I know it's a long shot ( being a Brother and long-gone EDM line, but has anyone ever seen this or have any idea perhaps?

Thank You

I'd do a visual check with a good magnifier of the solder joints on the boards. You are looking for any cracks indicating a "cold" solder joint.
The next thing to do is swap the DC PCB board with a known good one. Some of the boards were interchangeable with the HS3100-5100.
I have two HS50s. One is running. The other one, I'm just waiting for a good excuse to make it a parts machine.
Regards, John