AES with the closed captioning.

[acvila-de-munte]

We have an asset with added text track.
When we try to stream the video on ios/mac devices without content protection everything is fine and user can see closed captions. But when I turn on the content protection (now we modify azure response via hls proxy) closed captions are not rendered. I suspect that something should be added to the proxy to render closed captioning but can't get what exactly.
@mingfeiy do you have any idea how to resolve it?
Thank you