Can't set clip or mixer group on AudioSource

I can't set an audio clip or select audio mixer group on AudioSource using 2017.3.0b2.
The AudioSources I've created with 2017.1 works, but I can't create new ones..

 

If you think you found a bug in Unity, I recommend to submit a bug-report following the advice in this document.

Using the bug-reporter seems to be an important step, because it makes sure the report is in Unity Technologies bug-tracking pipeline and has to be processed at some point. Using the forum is often used to add to a little more attention to a bug-report, but does not replace submitting the bug-report.

It's from advantage to attach a project to the bug-report that UT can use to reproduce the issue and test their fix against. The easier an issue can be reproduced by QA, the more likely it is to get forwarded to a developer, who might or might not work on a bug-fix for that at some point.

After you submitted the bug-report, you receive a confirmation email with a Case number. UT often asks us to post the Case number in the forum thread, which allows them to find that bug-report if they look at your post.

Following these steps will increase the chance that UT is looking at your issue tremendously.