Shotcut Suddenly starts to freeze

The variable frame rate might be the issue with this file. In Shotcut, there is “Convert to Edit-friendly” which may help, and depending up on the level of conversion it may take some time, and considerable disk space.

shotcut_2021-06-28_16-58-54
shotcut_2021-06-28_16-59-05

Depending upon the Video Mode that is set, there might be a problem with multiple files with different FPS.