I noticed in another post that you can do an offset recallibration, how should I connect the input during this, to a probe x1 or x10 with the tip grounded or with a 50 Ohm terimination on the BNC or with the BNC open?
Please try the offset recallibration:
Turn off the unit
While pressing the menu button > turn ON the unit
Offset callibration should start (see screen) release menu button
Callibration should indicate “pass” > then turn off the unit and back on