After the PPK II had been stored for a long period of time, it was recently taken out to measure current. It was observed that, regardless of whether Source Meter mode or Ampere Meter mode (with an external 3.3 V supply) is used, the voltage drops by approximately 1.5 V after passing through the PPK II. Under no-load conditions, when the output voltage is set to 3.3 V, the actual output voltage is about 3.1 V. Could you please advise on what might be causing this issue?