Did you investigate? Did you find out something?
I still cannot open any video from VK.
Also I cannot open this links from another site:
https://cdn-e2.streamable.com/video/mp4/qt2v.mp4
https://cdn-e2.streamable.com/video/mp4/mwwj.mp4

Very often I receive this sentence: This browser (Opera) does not support video playback.

I can't send you problematic videos because all videos are problematic to me. Here are some of them.
https://vk.com/video-93808317_456240077
https://vk.com/video-63758929_171104490
https://vk.com/video-68782962_171745184
https://vk.com/video-51189706_456240202
https://vk.com/video-53193953_456241393?list=05ea8fe04023a2b7d7
https://vk.com/video-111527168_456239074?list=ed4c78b8d9ea8b3a58
https://vk.com/video-59555806_456239021

I wrote first to VK support:
Cannot load and playback video
I use Opera for watching videos from VK.com. In Chrome and Mozilla everything is ok, but in Opera there is a problem: "An error occurred during loading. Please try again later. Error code: 4"
I uploaded new version of Opera (39.0), and new Adobe Flash Player but it happened the same.
VK Support answer:
Browser Opera does not support this function now.
Please use the another browser.

My questions to Opera support:
Is it truth? What can I do? Can You fix it?