What style of output connection is on this YTO? Not whether it's SMA, but how it's mounted to the body. If it's a barrel type screwed into a threaded hole and locked with a nut, you can as a last resort try rotating it, a little at a time. I have an old HP YTO that had way low output because of intermittent connection inside right at the connector. When this happens, you have a tiny capacitance in series with the output, so only a tiny bit of signal gets through, even though the guts are working. Sometimes you can restore operation by changing stress at that joint - maybe temporary, but doable. If the YTO is of a type of construction that can be opened up, it may be possible to actually fix it with soldering or silver DAG.
If you manage to "fix" it by adjusting the rotation, the trick is to make sure that whatever final outside connection is made, can't stress it back to non-working while tightening it up, so it takes careful assembly. Keep in mind that every time one of these YTO connections is undone and redone, for diagnosis or experimenting, it adds to the wear and tear. This is why simply swapping out YTOs can succeed or fail, depending on what happens with marginal connectors.
I'm guessing that you may have two good YTOs if you can restore their connections.
Ed
