When i will return to home i will try with acetone (i was usually to clean it wit alcohol but i forgot to clean the platform in the last prints) but this will fix also the slided layers problem?
EDIT: For the layers problem i found this on the forum, could help for my problem?
This can be caused by a few things:
The filament spool doesn't rotate freely during a print, putting too much force on the motors.
The part is too large for the build surface and/or improperly positioned. In this case the extruder may bump into the end of the axis during a print, causing the layers to shift over.
The flow rate is too high, causing blobs of plastic to build up on the part, eventually causing the extruder to get caught.
An improperly set trimpot on a Stepper Motor Driver. The trimpot, which control motor current, could be set too high or too low. The four stepper motor drivers (X, Y, Z and E) are located on the motherboard and can be adjusted with a small screwdriver. This is a tricky problem to diagnose, so we recommend you contact us first so we can walk you through it. Here are some general guidelines: If the current is too low there may be no indication except layers shifting in the X or Y direction. If the current is too high: in addition to layer shift you you may notice an slow, audible click when the printer is powered up and the motors are enabled but not moving. Gently turn the trimpot clockwise to increase current or counterclockwise to decrease current.
I had to make this adjustment for my z axis because of the same problem you are having. It was debatable if cooling the board or adjusting the trimpot solved the problem. You can also measure the overall height of your print compared to what it is supposed to be. If it is too short, it is likely you are having some sort of overheating issue.