Argh, suddenly the object snap stopped working for placing the center-handle in my viewport.
Moving the handle it snaps only onto objects in other viewports, but not to objects in the current viewport.
Then after placing the handle, (without snap) when i move the viewport, snap works as expected…
Did you turn off Object Snapping?
No, it’s on, else the snapping woud not work when moving the viewport.
SOLVED:
The viewport’s style was showing only faces, no lines. (used for wall hatch).
I had to temporarly switch to a different style to get snapping.
Could have sweared this DID work with my hatch-viewports before… but probably not…
Snapping requires edges and endpoints to work. Turning off edges in the style will cause what you reported.