I am leaning toward your idea of something loose in the 4 in 1...I have been all over this little chopper, and just do not understand...I just had a successful flight, although all my trims have changed, charging now to try it again and see if there is a repeat. Stands to reason, loose connection, bad solder joint..
The antenna situation is interesting, although I am not convinced this is a glitch from interferrence rather than a potentetial break in a circuit.