Blown Finals?

I can key my mic with no antenna hooked upand use a rubber band to keep it keyed.Go have a cup of coffee ,come back and my finals will still be ok.I've don't it just to prove a point.

 

Could you elaborate on "backswing", Iv'e never heard of this and I seem to be having the same problem with an older Uniden. In the afternoon after it's been on for 8 hours it will stop transmitting and the meter will go backwards. No antenna light and the receive seems to drop off. It I shut it off for about 5 minutes it works fine the rest of the day. Audio booms out normally.

BTW stock Uniden PC78 LTW & a Wilson 2000 Trucker antenna, SWR's always have been 1.2-1.4.