If the spinner is supposed to run on 3.3v and you fed it 5v, you may have burned out one of the LEDs or phototransistors. 
These aren't true optical arcade spinners, so they don't work that way. There's a magnet and a hall effect sensor, which needs to be interpreted to get dial position (good possibility for the introduction of lag/inaccuracy), so no photo sensors.
If voltage was correct, you would need to look at the means of connection. This requires a bit of skill with a meter, or in the case of an incompatible signal, an oscilloscope, to see what is happening. If being connected to 5v, and you got lucky that nothing fried, it could be changing the voltage reference used by the analog interpretation circuitry.