I am also facing the same X-axis shifting issue. The build area of mine is 400mmX400mmX250mm.
As you see the attached pictures, the printing is shifted to left on X-axis. (latest firmware and recommended slicer settings are used.)
Actually the issue is disappeared when the feed rate is reduced by half. (printing speed 15mm/sec)
After several trials and errors, I find it is caused by the shaking of the head.
If the Z height is too tall, head is far from the middle and it is weaken from the rapid movement.
Do you think my analysis is reasonable? If so, do you have a recommended Z-axis height?
And could you let me know Z-axis height of your printer? Your printing result(corner.jpg) seems excellent.
Thanks in advance.