WEM Mk4 Copicat - low volume output

[Bushbaby]

All,
I spent a lot of time cleaning the heads (wiped with IPA etc) , replacing the old 1/4" jack plug (it was just a weeny bit bent) and generally cleaning the unit up (and a new tape). I tried it again today and .......it has finally got an output! It was reasonably ok for about 5 or so minutes then started to become more and more distorted. When I did clean the heads, yes indeed they are very worn. Do I assume now that it that the heads do need replacing as a initial step?

Best Regards