The Fritzbox has been in use for a year with no sign of these issues until a couple of weeks ago, so that seems highly unlikely.
Try another router and find out?
The fritzbox has a firewall VERY sensitive to ICMP pings.
It could have had a recent firmware update that is only now affecting your BQM or your ISP could have their own monitoring running on the line affecting it.
Some Fritzbox's will happily run with 1 BQM. Mine does. If I try run a 2nd BQM the Fritbox either shows packet loss of completely blocks ICMP, showing as full red sections on the BQM.
I would put my money on it being the Fritzbox, especially with it only showing in the BQM and not in actual use.
Edited by j0hn83 (Tue 06-Sep-22 12:39:00)