4 channel amp

I have an MTX RT4340 4 channel amp.  Recently the left front signal was no longer being received.  I have changed crossovers on that side and still the same.  I have checked the connections at the amp and all other connections and they are fine.  The signal is not completely gone but after a few minutes the signal will come back and then go away again.  Is it possible that only that one channel would quit?  Any suggestions?? Could it possibly be the left RCA cable (left front signal) that is broken or not functioning?

Check the amp's solder at the RCA connection on the board.If you have a cold solder this would happen.

Could you explain what a "cold solder" is.  If the connection is a cold solder how would I go about correcting the problem?

thanks for your quick response.

A cold solder is when the manufacturer does not heat up the contacts of the wires, connectors or RCA plugs long enough for the solder to completely adhere to the metal. After time, this connection comes away from the board causing intermitent sound or even crackling of the speakers. You have to open up the bottom side of the amp to see inside the amp and look at the RCA connection. If you push on them and you see the solder ( silver metal ) come away from the connectors you have to re-solder the connection.