prior to 2.320 and after 2.347, the "Schedule now" button on the project table view is animated when the project is in the build queue but not yet scheduled.

See here: https://user-images.githubusercontent.com/13383509/166511500-7aebe7e9-6b21-4f26-bc80-af3e1e935632.mp4

This was done to highlight the fact that the build of the project has not started yet, but will be as soon as possible.

drulli mentioned on https://github.com/jenkinsci/jenkins/pull/6534#issuecomment-1117319391 that this state should be highlighted differently.
We need to find a better way to display the fact the project is scheduled to be build, but the build has not started yet.