Marantz 6110 TT - spinning fast

So my little vintage setup was working perfectly ........ 20 albums in and then all of a sudden my TT is spinning fast (around 38 measured with Turntabulator). Seems this is not a normal problem for the Marantz cause all the looking up I?ve found is about it being slower not faster. It also doesn?t seem consistent because a quick switch from 33 to 45 and back again fixes it for around 30 seconds and then starts spins fast again.

Any ideas on what this could be. Also a complete newbie, so even if it?s something normal to check please let me know.