What could be causing this issue? (motor stops)

[Demxsr]

There are several reasons that can cause this.1. The linear bearings could have debris causing them to miss steps.2. The Smooth rods are lubricated with a grease instead of a light machine oil3. The smooth rods and bearing are binding due to not being correctly aligned.4. The stepper motor Driver module TMC2208 needs the V-Ref adjusted.

The main issue is the X or Y motor stopping randomly during the print and not starting up again. Or both stopping at the same time before the print is finished. In the first picture 1 motor stops, while the other kept going and the printer kept extruding, so you have this huge blob line. In the last picture both X and Y motors stopped at the same time mid print, and yet the printer kept extruding as if the print was continuing normally.I only brought up the miss step because it only seems to happen on prints where later down the road one of both of the XY motors will stop for the rest of the print, while the printer keeps going as if no error has happened.
It was brought up that the stepper drivers could be overheating. But I have heatsyncs on all of them with a fan blowing directly across them, and they are barely warm to the touch during a print. So I don't think that is the issue.

[Roberts_Clif]

Did this CoreXY machine come with the firmware installed or did you choose and compile the firmware yourself.
If you choose and compiled the firmware what did you choose?

[Demxsr]

Did this CoreXY machine come with the firmware installed or did you choose and compile the firmware yourself.
If you choose and compiled the firmware what did you choose?

It could totally be a problem with the firmware, I compiled it myself. Its a hypercube evolution that was a complete DIY build. The failure occurs about 40% of the time on prints longer than 5 hours. For shorter prints, they finish just fine. So assumed it wouldn't be a firmware issue. But I'm really not sure what in the firmware could cause that.

[Roberts_Clif]

This could be a thermal issue, try cooling the controller and Stepper motor Drivers.
Also if you happen to be near the 3D Printer after a few hours carefully touch the Stepper motors to see if they are overheating.

[Demxsr]

This could be a thermal issue, try cooling the controller and Stepper motor Drivers.
Also if you happen to be near the 3D Printer after a few hours carefully touch the Stepper motors to see if they are overheating.

everything is barely warm to the touch. I have heatsyncs on all the drivers with a fan blowing directly across them. Motors are not warm either during prints.

[Roberts_Clif]

You are correct this is going to be a tough one.