Commit button sometimes inactive

Occasionally, the Commit button in the Git Commit form stays inactive despite that there are selected files for commit and the commit message is not empty. This does not change if you switch between windows within QtCreator or between QtCreator and another application, or if you select/deselect any files to commit. Ctrl+Enter hotkey also doesn't work. As a result, there is no way to commit the changes. See the attached screenshot.

This does not reproduce reliably. In fact, it happens rarely, but I have encountered this more than once, on different machines. It seems, this happens more often when there are a lot of files that are not added to the git repository (i.e. untracked files), which triggers QTCREATORBUG-18206. Upon initiating the commit, QtCreator hangs for some time while it scans the filesystem, after which it displays the commit form with the inactive Commit button that doesn't become active.

This is not new to QtCreator 4.15.1, it has happened in past releases as well.