Ender. Happened back in the days with a 3v2, the stepper drivers on the original mainboard overheat, causing it to ‘miss’ steps.
Replaced the MB with an improved version, tuned the vRef and never had any issues again.
You might look into tuning the vRef for your machine.
Yes, as an alternative to klipper -this really is your end goal - use the firmware by mriscoc, it is really nice and robust.
Gives you more options and the results are better than the stock fw.