Hi I had a similar thing changed the battery for a larger capacity and also change the radio to 2,4ghz ,Planet 5 are very cheap .now no problems . I think it was mainly the battery,  but the radio I was using was also 27mhz and they do interfere  with each other am/fm ,if there the same frequncy .YHR is right the battery drop off dose cause some funny things to happen,Dont use the smoke unit they eat batteries for fun.

  regards pete