Were you getting any glitches when using the PPM Hitec reciever?

If Yes, then it probably was an interference related problem.

If No, then I would say it was a reciever problem.

Remember, PCM is there to make it safe for people, not to save RC aeroplanes from crashing.

I fly in Brisbane on 36Mhz. I have had countless thousands of flights on PCM without a problem in pattern models. The PCM technology has been around for a long time and is sound its probably your equipment which isnt. I would definetly put the sledge hammer to that reciever. I am sure that the cost of a replacemnt reciever is minimal compare to your loss across 2 models.

Peter