Qt Core contains prefix path to Qt installation directory. In static builds, qt_prfxpath is used to find location of qtlogging.ini file which points to Qt installation directory. When Qt had been build to a location that is on a removable drive on a machine where application is deployed, Qt tries to read the file on startup and Windows shows an error message that "There is no disk in the drive. Please insert a disk into drive xxxx."
Problem can obviously be fixed with a hex editor, but it would be nice if windeployqt also work on static binaries to fix this like it does with dynamic builds.