Issues with turntables picking up speed when trying to time start off. It's hard to match beats when the table does not start on cue or slowly try to catch up to speed. What's wrong with them?

This seems to be a pitch control issue. controller,
replacing \t,could be worn over time,
SL1200 Technics - if you want a solid long lasting excellence of sound reproduction for many years to come,

I had the same pitch control issue,
happened on one of my decks so I replaced the controller and good to go from there,

Another important tip -
never lubricate the controls sliders with any thing apart from the correct greases or oils applied by the manufactuer,most people dont think of the damage caused by the cleaners they use ,some aerosols eat away the fine oil that lubricates the pitch control sliders making them dry and brittle eventually cracking producing odd random performance issues,

hope this helps,cheers Misterdj