well it seems that every thing is in order (minus the hot elec. smell) I don't know what to say the heli is lifting off at the right amount of throttle and everything... try making it hover at 3/4 throttle that might help a bit and release a bit of strain.

just a wild (and random) guess is that the tail rotor belt could be tight and causing a bit of problems i don't know this does seem strange though. also how hot are the batteries getting?