@drw: Thanks! Your hint pointed me in the right direction. Found it, adjusted it, everything is fine! For anyone with the same problem that any rollers are loose: First, for adjusting the eccentric screws you need the #10 wrench. Gantry rollers: Look for the lower roller. Behind it, there is a long #10 nut which is the eccentric adjustment. Turn it with the wrench until it is fixed. Please check that it's still easy to move the print head. Table rollers: Uninstall the display first. It's easier to reach the eccentric screws without it. Look under the table from the front. On the right you see two long #10 nuts which are the eccentric adjustment. Turn them with the wrench until the table is fixed and still easy to move. Done!