I posted very carefully and checked the embedded link. It worked.
Subsequently the link was reported as broken by another user. That's odd, I think.
Turns out that any subsequent edit to the post results in the link getting broken. Let's test it here.
Original link - I will subsequently edit the post and add something. It will be the line "Added." AND another copy of the link.
If I am right this should result in one broken link followed by a good link.
First link.
www.flightradar24.com/blog/wp-content/uploads/2018/10/2018-035-PK-LQP-Preliminary-Report.pdf
Added.
http://www.flightradar24.com/blog/wp...ary-Report.pdf