If you’re here because the playhead is doing some sort of dance – 6 frames forward, 4 frames back, repeat – and you use some sort of non-standard audio interface (In my case Voicemeeter Banana) make sure that audio interface is available and in the case of a software interface make sure it’s running.

Incredibly weird effect if it’s not running and you try to play the preview screen. Anyway yeah that might be the issue. Start Voicemeeter Banana (if you use it. Replace software with the one you use).