Tecnodec w/HR PSU - Speed Problems - Help?

I own a Michell Tecnodec w/HR Power Supply. To set/check the speed I used a KAB Stobe disc.

I set the speed perfectly using the HR PSU. Then, I turn off the motor and re-check and the TT is running slower. Actually, everytime I turn off the motor and switch it on again the speed is different. If I leave it alone for 30 minitues the speed goes back to the original (where it was set the first time). It's not major maybe 0.5% variations.

This concerns me a little because this means when I listen to a second, third record the speed will be different than that of the first due to shutting down the motor to change an LP.

This also happened with the original cheaper PSU.

Is this a normal occurance with DC motors?

Thanks guys for any help,
Balance