Layer shift on Anycubic Mega S HELP!

[Brent Carlin]

I am having an issue when printing a job on my Anycubic Mega S; early on in the job (roughly 1hr into an 11hr job) I'm getting layer shift on both the x and y axis, roughly a shift of 2-5mm. It happens at this stage and then is perfectly fine for the rest of the job. Any suggestions on how to fix this would be welcome.

 

[VeNT]

any movement in the rails at all?
I'd ask on the Anycubic reddit tbh they are normally helpful

 

[Scougar]

I have been having layer shift only for big flat areas where blobbing occurs and knocks the nozzle. What is going on in that area of the print?

Weird to have both x and y, so I am doubting belt tightness.

EDIT: I tightened my Y-axis belt a bit more, and haven't seen layer shift since, but that might be luck.