Aging electrolytic caps are more often implicated in speed stability issues. My Sony exhibited same problem, speed drops resulting in a warbling effect. Replacing caps (not all, just the electrolytics) and cleaning the speed pots corrected the problem. My Denon has also been recapped, but by the previous owner. Recapping and cleaning seems a de rigueur thing when acquiring older DD's.
Reanimated vinyl enthusiast circa 2015...
#1 Denon DP-80/Kiseki Purple Heart NS
#2 Dual 721/Dynavector 17D3
#3 Sony PS-X4/Pickering XV-15/625E
Amps: Marantz PM11S1, VTA M125 Monoblocks
Speakers: Tannoy D700, SVS2000 sub