Mesa/Smart Serial errors

So, I've got my machine running, on a basic set up. Every once in a while SmartSerial stops.I get errors 13 (Communication Error), 7 (Too Many Errors), 3 (Timeout), the SmartSerial Port 0 will be stopped. Obviously this stops the machine. I currently have the processor on the arm and the 7i77 in the cabinet. This means I have to run a 10 ft DB25 cable, along side the 120vac wires for the computer and the display. Do I need to relocate the computer into the cabinet? There's not a whole ton of room in there. Is there another cause of these errors? I'm running a 5i25/7i77 combo.

Thank you

There have been a couple changes that improve sserial noise immunity in the last few years
Are these recent cards? if not the 5I25 should have its firmware updated
Also you should use the latest version of LinucCNC as its driver handles occasional data errors
more gracefully. If you have the latest firmware and LinuxCNC, another possible problem
is low 5V on the 7I77
( The 7I77 should have a local 5V supply and the 5I25/&i&& should be Jumpered for this )

Cards were bought around 18 months ago, definitely more than a year ago. I reflashed the 5i25 about a month ago, the 7i77 has a local 5v source that hasn't given me any trouble on the other 5v items on it (limit switch board) and I'm running LinuxCNC 2.7.11. I'll measure the 5v to see if it's saggin'. I couldn't even get 2.7.6 to run.

Okay, So I moved the computer closer to the control box and switched to a DB25 cable that wasn't run parallel to 120vac. Ran several programs several times, no SSerial crashes. Is there a way to shield the AC wires so they don't interfere with the data? The DB25 is shielded, but it's possibly not grounded on either end. If there isn't a way to run AC and DB25 alongside I will have to figure out if I can get away with twisted pair and shielded cat6 running alongside the power for control panel switches and the handwheel and putting the CPU in the cabinet. I know there was AC run to the pendant before, but the processor cards were in the cabinet. Also the AC to the pendant was twisted, now I'm running parallel conductors.

Shielding the AC wiring should help,

Another thing to try is a line noise filter