I expect Mr. Hennessy will be along soon.......
Otherwise, if you fancy a bomb proof upgrade, here's what I did:
https://vintage-radio.net/forum/showthread.php?t=54342
You may well have a whiskery output transistor or leaky capacitor somewhere- you've sorted the dodgy pots. T3 does thermal compensation for the output stage- pretty much any small signal Ge PNP will do.