Ender 3 V2 Intermittent extruder motor and nozzle overtemperature alarm

I have had my Ender 3 V2 for a a few months. Done the normal quiet fan mods, upgraded the extruder to a Titan clone 3:1 geared, and then updated the FW to Marlin 2.0 +bugfixes as I had to increase the max extruder e-steps. Its been working fine for a few weeks after the last mod as above with no issues.

I was recently doing a long print using the max bed. I did a slow first few layers, maybe @10 hours in, the infill extrusion stopped (it was infilling the over the whole footprint of the bed at the time). I dont mean it started clicking, popping and slipping on the filament, or a broken filament, because the nozzle was too close to the model. I mean the Extruder motor just stopped turning at all. The extruder has a large gearwheel so its obvious when its going round, or not.
I disconnected the extruder plug and plugged it into the old extruder motor and that didnt turn either, so I guess the issue isnt the motor, its more likely the stepper driver board had quit driving the motor. Power cycled the printer and all was well again. I temporarily gave up on that print and in the next couple of days I printed a few shorter prints with no issues.

A few days later I had tweaked the same large model and tried to print again. Once again at approximately the same sort of point in the print the extruder motor just stopped turning. I power cycled the ender and the extruder was back working again.
Annoyed, and because it was a pretty simple shape I managed to splice the second half of the model onto the first half with a reslice and a bit of Z offset tweaking.

But a couple of hours later the nozzle overtemperature alarm started going off. A few power cycles and it was still going off so I though the printer was dead.
I powered off for maybe 5 mins and then it all came back on ok. Spliced another part of the model and again after about another hour I had the same nozzle over temperature issue.
Now I have occasional nozzle overtemperatures. I stripped the hot end to check for a loose fitting on the thermocouple no issues found, opened the underside to check the connections on the main board, all looks fine. With the ender powered I tried waggling all connections, to induce the fault, no issues found.
The overtemperatures can now happen either part way through a print, or just immediately after switch on at the mains without the heaters even being on.

Anyone had a similar experience, anyone have any ideas? Should I just get a new main board and hope for the best??

Could it be main board going intermittent due to over heating ?

Thanks I hadn't really considered that. I upgraded all fans with quieter ones as the first upgrades I did months back. But when the faults happened I was driving everything at full tilt doing 100% fill over a number of layers over the full area of the build platform so maybe the new fan doesn't shift enough air. I will look into that.

I took Gambos advice and increased the fan airflow onto the main board. Actually I tweaked the regulator voltage a bit. Its a 5V fan but I increased the reg to 6V. I guess it may fail sooner with being marginally overdriven. But no repeat of the failures seen on the Ender so it may well have been overheating.