Welcome munocit ☆,
I understand how frustrating it must be to record for nearly an hour only to find that the saved video is 19 minutes long.
If you used Snipping Tool, please first check whether another copy of the recording exists:
- Open File Explorer.
- Select Videos > Screen Recordings.
- Look for any additional MP4 files created around the time you made the recording.
- If you find one, check its duration before making any changes to the existing 19-minute file.
Besides, you can try repair and update Snipping Tool
- Open Settings > Apps > Installed apps
- Find Snipping Tool, select the three-dot button, and choose Advanced options
- Select Repair. Do not select Reset yet
- Open Microsoft Store > Library > Get updates, and install any available Snipping Tool update
Also, please let me know whether the recording appeared to continue normally for the entire hour, or whether you noticed the timer stop, pause, or Snipping Tool close at any point.
Looking forward to your update.