Video Preview Not Playing or Lagging
If the video preview doesn't play, it's usually cause because the file contains variable frames i.e., it's a Variable Frame Rate (VFR) file.
To confirm this, you can use the Variable Frame Rate Detector within TimeBolt in the menu bar under Tools > Variable Frame Rate Detector.
This tool will analyze your file, confirm if it's VFR and give you an option to re-encode and fix your file.
Once re-encoded, the file should play normally.