Hi, recently I have a problem with a N5230A PNA - the amplitude "jumps" with 3.8dB without any obvious reason. This happens on a casual basis, but the change is always the the same, 3.8dB, and then back to the initial value. This jump is clearly seen on the display and it affects both corrected and raw data. At the moment I have a short cable connected between both ports and I'm reading +2dB IL. Can someone what's the problem with the PNA?