Are channelings always reliable?

Over the years I encountered quite a few channellers. Some of them were truly amazing (for a while). At times I also receive information from within, especially when it concerns assisting others.

However, there is a phenomenon I observed with all the channellers I new personally. Each and every one of them started as a genuine channeller, who channeled amazing things from very high sources, at times from probably the highest source. Each one of them started to gather fame, or students, or both. Some time after that happened, they stopped receiving genuine messages. I assume it is because of their egos swelled, due to their fame and students' admiration. So, having fame and/or students but not having genuine channellings, they started to fake it - at times knowingly and at other times unknowingly.

Once I was a student in a channelling school. The teacher/channeller was a very honest person in his personal and spiritual life. One day he took me aside and asked me to give him a "reading". What I received from within was that he stopped channeling. I told him that and he acknowledged it to be correct. I had the impression that he suspected it, but wasn't sure about it. He acknowledged what I told him out of (probably) his responsibility for me as my teacher. (However he didn't stop giving readings and he didn't close the school, not for a while).

Other channellers didn't know they stopped being a genuine channel, though I could tell it for sure, because of they delivered erroneous messagees.