Steps to reproduce:
1. Create new project
2. Add cube to scene
3. Use camera tool to align view on Y axis (in scene window top right corner)
4. With middle mouse button pan view for 10-15 sec.
5. Rotate view

Expected results: cameras pivot point didn't moved after panning. When rotating cameras view cube is located in the middle of a screen.
Actual results: cameras pivot point moves after panning in orthographic view

Note: The distance cameras pivot moves depends on how long the camera was panned for. Not reproducible when camera is align on z axis.

Reproduced with: 2017.1.0b1, 5.6.0p2, 5.5.3p2, 5.4.5p1