Regular video playback stutters. Premiere Pro 2020
My Video playback on my Timeline and Source window stutter. The screen tears, the video's frames switch frames back and forth while there are no issues in audio playback.

There’s not much to go on, in your post.
If you can reliably reproduce the issue, please reach out to Support and provide files and step-by-step instructions on how to reproduce the problem; happy to pursue it further.
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Kevin Monahan commented
This is the situation related to the Audio Hardware Preferences. The user's solution was, "I had to disable the Audio hardware/default input. Set it to no input. Problem solved."
Preferences that are not set correctly cause this issue. The problem is there is no warning or help for an unsuspecting editor not being aware that a visual anomaly might be occurring by adjusting an audio hardware preference. It's the last place anyone might look.
This is a very common, yet frustrating problem for users.