Video clip in-points reset to zero after saving and reopening (Premiere Pro 26.2)

** EDIT : This looks similar to the 2020 timeline-shift bug where clips reverted to first frame after project relinking (Autokroma article). Same symptom — clips back at their original starting frame — but a different trigger this time: it happens immediately on save/reopen for any clip trimmed through a UXP panel. **

The problem:
When a UXP panel trims the start of a video clip on the timeline, the trim works correctly while the project is open. But when you save the project, close it, and reopen it, every trimmed clip jumps back to its original starting frame — the trim is gone.

The same trim works fine on audio clips. Only video is affected.

What I've noticed:

• This happens on regular video clips and on multicam clips — every video track item is affected.
• It started with Premiere Pro 26.2. Earlier versions handled this correctly.
• If I use the razor tool (C key) manually, those cuts survive save/reopen just fine.
• If I use the keyboard shortcut to move a clip up a track manually, that survives too.
• Only the trim happens through a UXP panel that gets reset.
• Locking the track doesn't help — the trim still resets.

Why this matters:
Any extension or panel that automates timeline editing for video — multicam roughing tools, scene assembly, ad timing tools — produces results that look correct on the screen but quietly break the next time the editor opens the project. Editors don't notice until they come back the next day and find their work undone.

To see it happen:

1. Open a project with one video clip on V1.
2. Use any UXP panel that adjusts the clip's in-point (start frame).
3. Watch the clip update correctly on screen.
4. Save, close, reopen the project.
5. The clip now starts at frame 1 of the source — the in-point change is gone.

If the same panel does the same operation on an audio clip, it survives save/reopen. So whatever path the audio version uses internally is doing the right thing — the video version isn't.