Marmac sticky transmission shift knob

[akopac]

Hi Folks
I can’t be positive about the shifter manufacturer on this post. I live on a 1979 Morgan heritage yacht ketch. I’m currently anchored in North Tonga. My engine is a Perkins 4.108 with a velvet drive transmission I rebuilt last cyclone season and both work flawlessly.
The black shifter engaging knob gets stuck pressed in engaged occasionally at the binnacle Lately. I have found I can disconnect the shift cable below. And shift the transmission manually fine. I took the Allen screw out in the shifter assembly and lubed inside and it helped, but it still does it occasionally. It’s a M-1093-D2 shift assembly. I’m hesitant to pull the assembly as I’m remote and there are no parts here. Anybody seen this before? Any houghts?