Are you still on the old rambo board? If so... you could have a bad board. I've had two of them go out over the years. I switched to the Duet WiFi and never looked back. Maybe you could send the board into Seemecnc and they could tell you for certain.
it's in your slicer settings... you can control the speed of the outside/inside layers. Its there to save you print time by printing the inside layers faster than the outside.
Sounds like you have a couple of numbers flipped around
I have a v3.2 that prints great well almost. when printing a 20X20 calibration cube the z height and X sides are very close but the Y side is off by .5mm
if i scale the cube up to a 40X40 the error scales with it. Z is spot on X is 40.04mm and Y is 41.2mm. does anyone have any ideas ?