I fixed all old posts.
This is so weird, because all I did, was to select the link in the post, alt-x it and re-paste it, and it worked after saving.
I didn’t add or retract, nor did I changed anything.
anyway, thanks for your help and your time @unlessgames
But the bad thing is that, everyone that posted a Twitch video link ( VCV Rack Livestreamers - Twitch, YouTube, etc ) in their posts will have to do the editing work, unless something is done by the devs I guess?