Sudden baffling Z axis issue on my A5S

Smappy

So My printer has been working fine for months, not a single issue since I got it. But then just yesterday, after a 50 hour long print which came out fine, it no longer works. When I go to print any file at all now, one of 2 things happens:

1. It prints, but it doesn't bother homing the Z axis first, so the printhead is suspended in the air spitting filament out uselessly as it moves. The Z axis works fine when I tell it to home and when using the auto leveling, but not when printing any file.
2. It prints, if I already homed the Z axis, but it prints completely the wrong file. I've tried multiple files that are on the SD card that worked previously, and every single time it prints a different one, seemingly at random.

There was also one time where it just kept moving on the X and Y axis endlessly until they were hitting the sides opposite the limit  switches and I had to manually switch it off to get it to stop. 

I'm very new to 3D printing and I have no idea how to fix this issue, because it seems to be an issue with the electronics of the printer (or the SD card, but I think that's unlikely). I know nothing about electronics, and opening up my printer would probably void the warranty, which makes me hesitant because I don't want to ruin it further.

Samuel Pinches

Welcome @Smappy !

I would contact JGAurora - this sounds very odd, nothing obvious comes to mind. Unfortunately, I don't think there is much troubleshooting we can really help with, except perhaps suggest trying a firmware update?

Is there a G28 start code in your slicer start section?