I placed a small mushroom in the scene and snapped the camera to the scene view to frame the mushroom (CTRL+SHIFT+F)
The gizmos glitches and scaled to half the screen when zoomed to that object afterwards.

To reproduce:
- download this project
- open the sample scene
- make sure that you have the camera selected and the Move gizmo active
- Rotate the view a bit
- If the gizmo doesn't appear large, select the camera, and CTRL+SHIFT+F

Cannot reproduce in 2019.1.0f1 or 2019.2.0a10
Reproduced in 2019.2.0a11