Check all arms

There is a PTFE layer on the magnets which prevents to much friction between the print head steel balls and the magnets. This layer can wear out and make the friction too high. This will result in bad print results and possible layer shifts.

Take one arm at the time between your fingertips and turn the arm around. If it spins freely it’s ok. If you feel it has friction because it stutters when turning around or  it’s totally not moving at all, please lubricate with PTFE again. You can alternatively also use PTFE grease between the magnet and balls.