I thought it might be a good idea to attach a mains adapter to my Z88 while exchanging data with my WIN box via Eazylink2 (I suppose the serial connection needs some energy...

Because this is of course more than 30 years old, I tried a brand new "after market" mains adapter (CJE) - but this triggerd a "soft reset" as well. After some investigation it seems (regardless which adapter or plug in order) that every 4th or 5th connection triggers a soft reset and one out of ten even "freezes" the Z88 completely - only a "hard reset" can save it from that state.
Is there anything I'm doing wrong here or might this be (a known?) defect of my Z88?