The bumping of the head at the end of the job happens when the machine “loses it’s relative position”. That can happen if you bump the head or the laser arm while the machine is turned on, or shift the head by hand while it’s running.
Or if it hits something or hangs up.
To clear it, turn off the machine and gently move the head to the “home” position. (Upper left hand, with the head over the gridded part of the tray.)
Turn the machine on, and let it run through the Start Up calibration…it should relocate itself correctly.
The problem with the prints might be a loose belt or pulley underneath the laser arm, or it might be a damaged V-wheel. To check the wheels, with the machine turned off, lift off the head from the carriage plate and inspect them with a flashlight to see if there are any cracks or breaks. Post a picture if you find anything amiss.
If you need to check the belt, there are instructions for what to look for here…