STEPS TO REPRODUCE
1. Launch popVideo 3
2. Navigate to Toolbar > Import File, load a mp4 file
3. Go to Playbar, use Mark In and Mark Out to set range, then click “End” button
4. Click “Next Frame” on Playbar

ACTUAL RESULT
It exceeded the range that created by Mark In/Out

EXPECTED RESULT
It won't exceed the range that created by Mark In/Out