A second video that replaces the first can disrupt a comparison even though both files play correctly on their own. On Windows, VLC 3.0 has settings that determine whether opening another item reuses an existing instance. Test both ways you normally open files, because launching VLC and opening from File Explorer can expose different behaviour.

Choose two harmless sample clips with visibly different opening frames. Label their purpose in your notes, such as original and revised. Close unrelated playback windows so that the test does not depend on guessing which existing window received the second file.

Check both instance controls

Open Tools, Preferences and select the Interface section. Under Playlists and Instances, clear Allow only one instance and Use only one instance when started from file manager. Save the preferences. These are the two controls identified by VLC's Windows instructions for this task.

Finish any playback you need to retain, then reopen VLC for a clean test. Open the first sample and pause on an identifiable frame. Launch another VLC window and open the second sample there. Confirm that the first window still contains the first file.

Next test the File Explorer route you actually use. Start from the same first-file condition and open the second sample through Explorer. The desired observation is another independent window, rather than a replaced item or an unexpected addition to the first session.

Make the comparison unambiguous

Arrange the two windows so their identities remain visible. Seek each independently to the relevant scene. A convenient side-by-side view is not evidence of frame-accurate synchronisation, so compare a clearly identified event rather than assuming both playheads represent the same instant.

Listen to one window at a time when checking speech or an audio defect. Two simultaneous soundtracks can create an apparent echo that belongs to the review setup rather than either source. Return to single-file playback if performance becomes uncertain, and establish whether the issue persists there.

Record which opening path passed and which setting was changed. If you later prefer one-window behaviour, restore that preference deliberately instead of leaving a future user to interpret every new window as a fault. The outcome is predictable file opening for this review arrangement, with independent controls and clearly identified media.

Sources: Official documentation.