Oscam strange issue

Got a strange problem my friend has his own server with just a few friends & family running one of the latest versions of oscam and using Mgcamd as the Emu on the receivers all channel work fine without any freezing but at certain times of the day the odd channel History 2 being one of the main culprit will become unwatchable freezing constantly and going off.
When the oscam log is checked it says (not found) next to the user yet all other channels are working fine sometimes it happens with the odd kids channel once channels are changed it says (found) again and it only happens on a handful of channels.
He has tried changing the version of oscam and using cccam receiver end the problem still occurs any help would be much appreciated thanks