Apple team has accepted that it is a bug and is corrected in IOS 15.1 (which is in beta currently) , so have to wait for official release of 15.1 for full solution on this.

A screenshot of Apple technical support team reply on this to our team is attached.

Feedback ticket submission was private and thus no option to share the link for it. Reason is that Apple is not supporting certain encryption scheme.

Unforuntately, this issue has also now started coming in Mac OS Safari 15.0

We have explored more and also found the cause of bug, a detailed bug report along with samples has been filed on https://feedbackassistant.apple.com/ The feedback ID is FB9646199.

We are facing this same issue in IOS 15 Safari with Fairplay DRM playback. Can we get a reply from Apple team, please help ? Since the issue is not in App, Netflix etc. are not going to report it but this has become a major challenge for website users of Fairplay DRM.