I assume you marked this as solved, and it might be, though from what I read, it sounds like what I was experiencing in multiple K1 Max printers. It would be printing fine, then all of a sudden it prints horribly, and I have been tracking it down to being related to a Wi-Fi driver issue. Even if you have not been using the Wi-Fi, it still has a problem: Problem with Wifi module affecting prints
I am not 100% sure your issue specifically is related, but it does sound like it and given that it took you down the path to replace multiple parts before you got it working again, is interesting, but I would be curious to see if the problem suddenly returns after a while. I am not sure if the problem is due to the helper script and running fluid or if the module itself just has bad drivers, but I if the issue returns, try a simple reboot, then re-run calibrations and then send the same print from your slicer where it had previously failed, and see.
I don’t know how technical you are and if you are able to check the logs, but if you know how, that would be great to know also.