Satellite background moves, roads don't

When I’m editing and click and drag on the map to move on, only the background satellite picture moves while the map drawsing (roads etc.) don’t. Of course, both should move together. Is that a bug in OpenStreetMap?

Please specify your editor.

Potlatch: The background image can be repositioned while holding the space bar and left click and move the mouse.
JOSM: Check if you’re in edit- or selcect-mode. There is a tool on the left toolbar to reposition the background layer:

I’ve noticed that sometimes the background layer in Potlatch moves without me holding down the space bar. I figured it was a problem with my own machine so didn’t make a bug report. For me it’s just a matter of closing the browser. It always solves the problem.