Back in October 2019 we reported that hotfix 2 for Prepar3D version 4.5 re-introduced a bug/feature impacting the doppler effect. Here we are, almost a year later, a major version update with 2 hotfixes already being released and it is still contained within the application.
Hopefully this will be fixed soon. In the meantime, you can still fix it yourself using the howto in our original article on the subject.