It sounds like there is a cold solder (improperly made connection *very common*) somewhere in the high power circuit somewhere. This will cause intermittent problems which sometimes go away when the unit heats up enought to expand the connections. STOP WIGGLING CONNECTIONS. If they are not broken you will break them by doing this. Before I climbed the mast
I would have someone competent inspect the xmtter. See if you can order a copy of the wiring
diagram from the manufacturer then bring the whole unit in to the local TV repair shop. A competent person should be able to at least inspect it and fix a poorly soldered connection. Or if it is still under warranty send it back to them let them deal with the headache. It'll cost you about the same either way. And if that fails, up up yo go. Good luck.