Cambridge Model 20 Issues

I am (I think) a proud owner of a model 20 which is driving me up the
wall. Yesterday, I was flying our clubs Discus B with my logger
attached under the glare shield. On my flight, after I was off of tow,
the recorder recorded what looked and was shown as engine noise. The
engine noise also showed up in flight for a couple of minutes. A
friend of mine asked if I had the gear down during my initial climb
and I did. I also dropped the gear to drain my bladder once. My logger
is translating engine noise for gear doors open. Am I the only one
with this problem? Is there a sensativity adjustment that can be done?
I have the question posted to Cambridge but they are close now so I
figured I would see if someone out there had the answer faster.
Thanks
Brian Iten
17