WEM Mk4 Copicat - low volume output

[Murphyv310]

Hi.
I'd assume that the heads are clogging the gap due to wear and abrasion of the tape surface. Obviously without seeing the unit in front of me I wouldn't like to give you the wrong advice as there could be more than one fault but as you say the heads are very worn so in essence they will need replacement anyway.
Good Luck.