I think you are right about ?fbclid, at least it seems to hint towards a facebook url.
And I did find that some facebook URLs do work with /l for example
http://facebook.com/l/healthyRewatching
https://www.youtube.com/watch?v=_JcasYsQ234 at 0:56 I see:
Which in text is:
12/20-8-18-5-5-16-12-21-19-20-5-14-20-8-18-5-5-20-9?fbclid=l
and decoded with a1z26 yeilds:
l/threeplustenthreeti?fbclid=l
To me that looks like a truncated "three plus ten three times three" which so far has been decoded as "missingtrack" ...
And somewhat intersting is
https://www.facebook.com/l/missingtrack yields "The link may be broken, or the page may have been removed."
That's notably a different result than a link that never existed, nonexistent links just redirect to the facebook home.
It's also thats similar to the other hint "qhLi2s6ss57" which as youtube url
https://www.youtube.com/watch?v=qhLi2s6ss57 yields "This video isn't available anymore"
So... are the answers actually missing links? I don't get it...there must be something else *scratches head*