Tvheadend

Hi, I was noticing that with the encoded channels in my case Rai HD in nagravision, after a few seconds of streaming on these channels falls 1 minute online 10/15 second off line and then reboots, it always turns around all the mixer channels that i am Stream. This thing does not happen in unencoded channels, i just keep it online without falling 10/15 hours i would say perfect, Am using the oscam api ... any suggestion? thanks