That is a really weird problem.
I'm thinking you might have accidentally broken your MediaIn node by saving a default that's making it look for media from the Media Pool, instead of loading it from inside the Fusion Clip.
Do this:
- In Fusion page, right click on the MediaIn node
- Choose Settings -> Reset Default
- Now go back to Edit and make a new Fusion Clip and test if it now works correctly
If that works, do this to fix any existing Fusion Clips that are still broken:
- Delete the MediaIn node
- Add a new MediaIn node
- Confirm it shows as being set to Layer 0, like this:
I'm 95% sure that's what's happened, because your symptoms shouldn't be happening by default, and it's working fine for me in 17.4.