On my PicoScope 3206 I have a constant offset of ca. 4 Volt on channel A even when short-circuiting with a BNC terminator. Channel B works normal without an offset. The offset is still there when a select AC. The amplitude shown on channel A is only half of the real signal ampitude. Probe (x1), scale (1,00) and offset (0,00 %) in PicoScope 6 are set correct. This offset can also be found on PicoLog Recorder.
What could be the reason for that big offset?