Reproduction steps:
1. Open the attached “BugRepro” project
2. Open the “Assets/Scenes/SampleScene.unity“ Scene
3. Open the Timeline window (Window > Sequencing > Timeline)
4. Select the “Timeline” GameObject in the Hierarchy window
5. Click on the “ExposedReferenceClip” clip in the Timeline window
6. Drag and drop any GameObject from the Hierarchy window into any reference field in the Inspector window or select any GameObject from the object picker in the Inspector window

Expected result: Reference is assigned correctly
Actual result: Drag and drop does not update the field, and selecting from the object picker displays the “Type mismatch”

Reproducible with: 6000.0.49f1, 6000.0.50f1, 6000.1.5f1, 6000.2.0b4
Not reproducible with: 2022.3.60f1, 6000.0.48f1

Reproducible on: Windows 11
Not reproducible on: No other environment tested