Reproduction steps:
1) Create new project
2) Create UI Canvas (Render mode: Screen Space - Overlay)
3) Create UI Image as Canvas child
4) Create 3D cube as Canvas parent
5) Move cube

Expected result:
Canvas should stay in place (because of Canvas Render Mode: Screen Space - Overlay).

Actual result:
Canvas moving together with cube.

Workaround:
Don't create parent for UI (make sure, that parent wont move).