If a model or part is in a folder in the Workspace, then mouse-drag selection will not work on the object.
Video demonstrating bug:
Pretty straight-forward repo:
- Create part/model in Workspace
- Drag-select it to verify you can do that
- Create folder in Workspace
- Place that part/model into the folder
- Attempt drag-selection
If bug persists, step 5 should show that the object cannot be selected.
Edit: To clarify, this is only for drag selection. Clicking to select still works. Not sure it matters, but this is on Win10.