Slow thumbnail loading blocks player UI

We are experiencing issues with the Cloudflare Stream player. The issue we have is that the player takes more than 3 seconds to be ready to play the video (iframe onload event fires).

Looking at the network activity it seems that this is due to the poster image (thumbnail) loading very slowly.

I have attached a screenshot of the network tab showing the thumbnail request. This does happen on consecutive calls to the thumbnail image (we are using signed URLs for the stream).

Example unsigned URL where it works fast and cached as expected:

It should not take 3 seconds to fetch this small image, even for signed URLs. Any advice how to fix this, without building our own player?

Any response from Cloudflare please?

We openend a support case and we do not get responses there either. Please, at least attempt to help us ?!