Compliments of the season to all
The only way you should 'seriously' see a slowdown of the platter is with a stroboscope on it. If the platter nearly stops, there's something amiss I feel. The delrin cam-lock as A70BBen referred to is spring loaded and pivoted at one side and shouldn't offer so much resistance I think as it ends the cycle with a slight 'clonk' as it engages into the rest position. (the Dual 1019 in my avatar currently is almost deafening at cycle end, so loud the 'clonks' seem to be - plenty shown working on YouTube of Garrards and Duals if you want an anal giggle and loudest of all seems to be the lab 80 which was incredibly heavily built but I digress...).
My suggestion now everything has been cleaned hopefully, is to run the deck at 33rpm for a few hours, just spinning away to itself so the motor gets nice and warm
the slight 'slippage' if there is any, may go all on its own if you're lucky...