Ah - do not raise the spindle! Your issue sounds like the clamp! Just order a type 5 puck. To test, use a small blob of blu-tack next to the rubber grommet on your existing puck, will likely fix it. You can also try turning the existing rubber grommet through 90 degrees so it grips better
(unless Theta replacement is available/cheaper?).
If it’s that, just order a Naim v5 puck
Search for blu-tac- then no need to glue. You’re just testing if that is the issue. Probably a piece of plasticine will do same job, but I’d use 3 small dots, without glue.
note that under the platter there is a small steel rod that is sprung loaded to hold against the spindle - be careful not to dislodge it if removing or priding platter...it pings off...and takes ages to find
I’ll share a picture of mine later - but won’t be until tomorrow now