ORIGINAL: Luchnia
Great catch! Just last week I had a similar situation and I even noticed something the week before. I kept hearing a slight variation in engine sound on my Pulse XT. I have flown the plane around 175-200 flights and I heard a small but noticeable pitch/vibration change and I had noticed the week before my switch on the side had two screws loosened. I checked my engine and she was smooth as silk and really could not find anything wrong. Well, I was flying it Sunday and I went to start it and noticed that the engine seemed to move back slightly. After further inspection I saw the firewall was cracked and would move about an 1/8 of an inch.
The point of this is that the sound or change in the characteristics of the plane was giving me an indicator that something had changed. Careful inspection is vital and is the real key to save planes. I do agree that switches are probably the weakest points outside of connectors. You have to make sure your connectors are vibration free and well connected or you will soon find out just how good they are [X(]
Along these lines, I never heard any noticeable sound, but my RTF PTS P-51 mustang had its firewall floating about 1/8" forward under power and when I bent it by hand. I took it to the hobby shop and asked some of the seasoned veterans of the hobby, and they recommended quickly sealing it with epoxy if possible. I did just that, and it no longer moves, however they were very surprised by it (I guess nobody should be surprised considering the discussions on here about the quality of ARF/RTF glue joints.... but they were). I've learned not to trust ARFs, but at my green/newbie level in the hobby, and considering my shortness of room in my college dorm/apartment, I certainly can't build my own planes (my most recent plane was built from a kit by a professional carpenter).