Video thumbnail not displaying

[coxde]

Steps to reproduce

1. Turn off "Autoplay GIFs and videos" option
2. Open a bridged room including videos.

What did you expect? A thumbnail inside the player frame.

What happened instead? The player frame is shown, but with black background. It can plays if I click play button.

Note: I enabled encryption.

Related: https://github.com/vector-im/element-web/issues/22791