5i25/7i77 communications error 7 and 14

Change the computer. Much cheaper and easier.
I had sserial errors with a Mesa 7i76E when running from a Lenovo T420S every 2 to 5 minutes, although the latency with Preemt-RT was good, and after several restarts of linuxcnc it would stop erroring and run hapily for hours. So i took that same SSD and put it in a Dell E6510 that has far worst latency, same instalation, it never stops comunication, ever. Ocasionaly i get an error about something or another, but never complete communication failure, so i never have to restart linuxcnc.
This is all for testing purposes, using 7i76E, have no problems with 7i92 and 7i77 but i have nothing connected to 7i77, just sitting idle and turning spindle on and off.
I would have changed the computer and moved on, preferably an older one.

They can be also caused by hardware faults, i still have a Dell Ltitude 6500 that has problems with nvidia graphic card causing huge spikes in latency and a mess when used for software stepping ( max velocity 300mm/minute with it, 1800mm/minute with anothe laptop on the same mill).
A long time ago had a desktop that took 25 minutes to start and starting any program would last forever, turned out the onboard sound card was gone the way of the dodo bird, even disabling it in bios did not fix it, it got to be usable with an add on sound card, but still to slow.
That is something that can be caused by any hardware that use IRQ's, power supply with dried out capacitors, bad memory etc.
Also some chipsets had huge problems that are not obvious during normal usage, namely Ali and Oli chipsets and rarely VIA. Havent seen much of them lately, but you should check just in case.