After I stumbled, by chance, on mirror 141.84.43.19 (being part of the
deb.devuan.org pool) being unavailable for a couple of minutes, I set a
script up checking TCP/80 availability for all of mirrors in said pool.

The conclusion is clear:
1°) 141.84.43.19 is the only mirror suffering from this problem
2°) This problem was detected with a high frequency, despite relatively
infrequent checks (1 every 5 min)

For this day only so far, 2019-07-17, at 1600Z, all the failed
occurences were happening at those times:
0050Z 0055Z 0100Z 0105Z 0110Z 0115Z 0120Z 0123Z 0145Z 0150Z 0155Z 0200Z
0205Z 0230Z 0240Z 0245Z 0250Z 0310Z 0410Z 0420Z 0455Z 0510Z 0515Z 0520Z
0535Z 0610Z 0615Z 0630Z 0640Z 0645Z 0715Z 0755Z 0800Z 0805Z 0825Z 0905Z
1035Z 1100Z

Hence the following questions:
a) Am I the only one observing this (ie someone else having set such a
check up with a check frequency relatively close to mine, eliminating
biases of my setup)?
b) If not and this a confirmed defect, would not it be reasonable to
remove said host from the pool until the maintainer can inspect what is
going on and act on it?

Bernard Rosset
https://rosset.net/