Repairable, absolutely. It's just a matter of how in depth and costly it will become. If it passes the hammer test, it's likely that it is not serious at this point.

Over the years I have tried a number of things trying to dry the wet transoms with Vacuum and relief holes,pulling in exoxies. but in the end always opened it as there is no shortcuts and replaced the wet plyrot with dry plyrot.

Wood is a natural water pump and is in natures recycling system,just add water everything else needed is present.

Think of it as cancer... cancer doesnt just go away and will eventually kill. The tumor needs to be surgically removed....