Has anyone had trouble with speed on their tt

Well, Syntax, you might be right. I have Expressimo Audio and it is working great as it checks its speed 500 times per revolution and corrects the speed if there is any drag instantly. If it ever needs tweaking at all, a laptop plugs in via USB and it can be calibrated to a strobe to the tenth of a rpm. TTW also has a motor system that has favorable review I have read. Brian of Expressimo also uses very precise machining and a great ceramic bearing on his turntables and they are leveled and balanced precisely. what system do you use?

just had an issue on a technics 1200, a machine that is supposed to keep perfect time. i swapped mats and was using a leather 45rpm small mat under a cork on cork spot mat. Was hearing sour notes and wowish kind of sonic. turns out the cork mat was slipping on the leather mat. i placed a rubber mat under the cork and all locked in. what would you call that as an issue: mat slippage?

Mosin is right.

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Kiddman, there are no motors or turtables with absolute speed stability. Every motor is subject to "kick & coast" - the effects of which cannot be completely removed. It would be nice to think it could be engineered to be 100% non-cogging but it can't.

Even high-tec radical solutions to compensate for inherent issues of suspended chassis tables such as the Kronos which uses counter rotating platters are still flawed because the basic engineering cannot be accurately balanced e.g. weight & tension of materials etc.

To give another example, an Avid Acutus would be one of those poor candidates you mention but I would cheerfully buy one today.

"corrects for drag instantly...."

Not possible. Instant velocity change to the correct velocity would be like a perpetual motion machine.

Fast correction = flutter.

Slower correction = wow.

Slow correction = drift.

All affect the music. Correction (servo circuits) are bad for this application. It's why no master tap machines used them, which is directly addressing the OP's stated problem, his DC turntable's speed problems. DC motors need servo circuits, and those are very compromised for this particular use, high end turntables.

Everyone thinks they have great speed stability in their turntables until they hear one that does, then they wonder why the stable one is so clear, so natural, so right.