The trick is to use a plastic/nylon washer between the prop driver and spinner. A friend turned up some for me from delrin. About 1.5mm thick. You could try a round servo output wheel drilled out to suit or cut some from some thin nylon sheet. The prop driver and spinner will bight into the nylon and it will never slip again. You may need a new driver if it has worn excessively. Tate’s should have these.

Cheers