Nuedno 12 when I play timeline my play head doesn't play smoothly

when I play timeline my play head doesn’t play smoothly. It suddenly jumps from one position to another. The timecode counter stops and in between and again starts. I can hear the audio with video but can’t see the play head position on timeline with reference to audio events.

Specs?

Windows 11 pro
i 7 6700
ram 48 gb
c drive 500gb SSD