Technical Forum issue: video embedding, rarely, does not work. (Bug?)

Bug in recognizing/using URLs of YouTube addresses? (Is there any logic in it?)

I was unable (September 2020) to upload and embed a YouTube video into a Forum post. I left it for a while, thinking I was doing it wrong and didn't understand. (I have now removed the temporary test-post). Then I did some experimenting. It turned out that the Forum editor DOES convert most URL addresses and (rarely) does NOT convert some others.
I then deleted my own video from YouTube and re-uploaded it. With automatically another YouTube link. The new link was recognized and embedded.
(See my recent post: "Corona Chorale - Polyphonic piece for piano 4 hands - Alpho van Cets").

Below are a few random links that DO work:

&ab_channel=AlphovanCets       &list=PLGmxyVGSCDKvmLInHxJ9VdiwEb82Lxd2E&index=5

 

and others that DO NOT work/embedd:

My former video-link (3 "copies" - now empty - shown here for the address text):

• &ab_channel=AlphovanCets

Some random link I found:

• (https://mixdown.online/en/how-to-record-audio-with-cubase-and-obs/)