dude!
my mobile devices have been doing the same thing and I've been tearing my hair out for a fix.
do we both (by chance)
have Mullvad VPN set on the router?
I have a SBC acting as router and every interface that goes to Mullvad has this problem.
I have other interfaces that arent forced through VPN and they're unaffected.
ill contribute towards a bounty if its the same problem.