CORS error in users and channels screens

When entering the /users/{user_id} or /group-channels/{channel_id} pages, 3 out of 4 times I get a red error banner of “Network Error”.
The page only partially loads, with critical info missing.
The Network tab on Chrome shows CORS errors.

Chrome browser on Mac, no network-related extenstions or ad blocks.
Sometimes refresh helps, most of the times not.

Access to XMLHttpRequest at '{user_id}/group_channel_count?state=joined&super_mode=super' from origin '' has been blocked by CORS policy: Request header field baggage is not allowed by Access-Control-Allow-Headers in preflight response.