RE: Why should I use a PCM receiver
After I posted I read your comment that you are running 5 cells. Not sure if it helps but while JR Rx are rated to 5 cells JR servos are only rated for 4 cells. If you are running JR servos with 5 cells could this be an issue?
I run most of my aircraft with four cells or regulate to 5V. I do have two 2M pattern planes running with 5 cells but I use Hitec rather than JR servos for this reason.