Transparent PNG sequence has a black edge

I want to export PNG image sequences from Animate CC with a transparent background. I am using "export video/media" because I want to animate objects using ActionScript. This passes the job to Media Encoder. Unfortunately, the transparency doesn't work as it should and the edges of objects are always black (please see attachments).

This problem is also described in this post from 4 years ago:
https://community.adobe.com/t5/animate/alpha-channel-video-render-problem-black-stage-coming-through...

The solution says that it will be fixed in a future update but that's not a solution and it's been four years!!

I would be greatful if this could be fixed. Thanks.