I'm pulling my hair out!!

Hi guys im New here so apologies if I'm bashful in my terminology with the following issues. But I am as the title says desperate. This printer issue has me pulling my hair out!!

I have a CTC 3D printer with a mightyboard atmega 1280 running sailfish 7.7 firmware.

I've had it for a few years now and have always used autodesk meshmixer and makerware to print my models. This has worked very well for the past few years nó réal issues at all. I've always been happy with my prints.

That was until a week ago. I bought an stl file online and split it into 4 parts as it was to large for my plate. The first print was perfect as expected no problems, but the next day when I decided to print the other 3 prints they would randomly start layer shifting. It would happen at different times in the print and never in the same place. So I did the usual checks,

I checked all the belts and pulleys
Checked the tension on the belts
Checked the vref pot
Checked the tool paths in the slicer software

All looked fine, thought maybe it was a bad wire on the x axis so I changed that but still no good.
Then it started to randomly print further to the left of the bed for no reason. But when I homed it to level the bed it would come in dead center... OK so now I'm really confused. I adjusted the offsets to account for it printing off center but it did nothing, it only showed my adjustment when I went to level the bed and it would now home off center.

I though OK I'll do a complete reset. So decided to reflash the firmware in replicatorG.
Worst idea ever! Now it starts homing incorrectly on a simple bed level check. Instead of going to the center of the bed it grinds and vibrates straight from its home position to the front of the print.

I did the calibration test in replicator G and it worked fine only goes wrong when I use the LCD control panel on the printer.
So next I erase the eeprom and reset the board to factory settings do a fresh install.
I check my home offset values and toolhead values are correct and go again.
But no... my printer does the same thing just grinds in the wrong direction.

Then randomly after I don't know how many flashes it comes alive again and I can print from RepG perfectly via usb.

But if I use my SD card it's off 8 mm to the left x axis and 5mm to the front Y axis??
It knows where the center of the bed is when calibrated and offsets are set but suddenly has a mind of its own when I go to print anything.

Again I checked everything mechanical and electrical. I ruled out a bad motor as I can jog the motors all day long with no problems at all.

So I started trying different slicer software and for some unknown reason as soon as I start printing with slic3r I'm right back to square one it's grinding in the wrong direction and there's nothing I can do as no matter how many times I flash the board, or purge the eeprom or reset any parameters it does the same thing over and over!!

I'm actually going crazy I feel like throwing it out the window tbh. I've spent 7 days non stop trying to get this to work like it used to. I've read the installation manual twice!! I've read dozens of forum entries and watched countless videos and I'm so disappointed.

I really need someone to help me find out either what's wrong with the printer or, if it's me doing something wrong?
A massive thank you in advance for any useful help.

have you tried a different sd card ?

sounds like it oculd be either the card itself or the card reader playing up.

Also as what you have is a replicator clone using x3g files - have you tried Flashprint as a slicer ?
select creator pro from the machine menu and try that.
https://www.flashforge.com/download-center

I find for the rep clones it's easiest the best slicer, particularly if you ever do dual prints.