If you build and run the attached test application while in Light mode then the scrollbars look fine, as expected (1a-light). If you then switch to Dark mode, the scrollbars are of the wrong colour (1b-dark). If you switch back to Light mode, the scrollbars are light again, as expected (1c-light).

Similarly, if you start the test application in Dark mode, the scrollbars look fine, as expected (2a-dark). However, if you switch to Light mode, the scrollbars don't have the correct colour (2b-light) while they do if you switch back to Dark mode (2c-dark).