mission control desktop animation bug

This has me stumped. When I slide between spaces on my 11" MBA (running current version of Sierra) in my main user account, sometimes the desktop background doesn't move the way it should.

The video attached illustrates better than I can describe. In the first part, you see the normal animation. The desktop background moves with everything else as I slide between spaces. In the second part, you see the bug: the desktop remains stationary, weirdly, while everything else slides.

If I restart, the issue corrects itself for a while, but always seems to return. It doesn't show up in any other account than my main one. Anybody see any similar behavior, or have any troubleshooting ideas?