Sounds like you have ruled out the slicer then. Does it look correct in preview mode?

Can you monitor the temps as it prints? I do wonder if there is a failing heater cable that's bending at a certain point and intermittently losing connection?

Does it do it on both extruders?

Try some test cubes at various points over the bed and see if you can work out if there is a specific area where the print goes wrong.