Based on everything that's been said, are you sure you extended your transmitter antenna before flight? It would explain:

- Why your morning flights went well but by afternoon you ran into problems (reached a point where you forgot to extend it).
- Why you're having the problem on take-off (at end of range with antenna down) but not on the bench.
- Why it went squirly but you were able to save it (at the threshold of reception).