As a signaller/gunner flying in many aircraft [Lancs, Lincolns, Ansons, Varsity, Valetta and Shackletons] equipped with the Tx1154/Rx1155 combination I can assure you that I never noticed any problems of this sort. The 1154 was a very reliable piece of equipment........although the aircraft Morse keys left a lot to be desired!
Hope that helps.
Robert H Mercer.