I have a problem with the Y axis shifting while printing. It will do it randomly 3 or 4 times during most prints. The taller the print the it dose it. It seems that it will only do it with this firmware I’m using the latest from here. If I flash to Wanhao firmware No shifting at all, Actually I have never had this problem until using this firmware.
I like this firmware as I am a patron here and the use of all the settings and LCD features.
In my experience, the Y axis on these printers is the most susceptible to shifting due to mechanical issues and unlikely to be cause by anything in the firmware with the default settings. If you have made any changes to the motor settings (jerk, acceleration, etc.) in the firmware from the defaults, I would recommend changing those back.
Mechanically, make sure your belt is properly tensioned and not worn, the bearings on the bed are rolling smoothly, that the Y axis rails are parallel, and that no cables are binding as the bed moves. You can also try adding a belt tensioner to help get any extra slack out of the Y carriage belt (I’m using this one: i3 Plus Y-Axis Tensioner (Wanhao, Cocoon Create, Monoprice, Balco etc) by benpatto - Thingiverse).
If everything check out mechanically, you can also try slowing your prints down. Before doing a rebuild of the Y axis, I printed at 40-50 mm/s if I wanted a clean print. Anything over that on a stock printer was pushing it in my opinion.
I will add that I also had issues with Y axis shift after doing an upgrade (forget to which version) and at first thought it could be a firmware issue, but once I stated checking things out, found mechanical issues (worn belt, and binding bearings) which prompted me to rebuild the Y axis (new drylin bearings in aluminum pillow blocks, adding pulley supports and belt tensioners, and a new belt). After the re-build, the printer has been working great and run my prints at 60 mm/s with no issues.