WG - sudden packet loss and dropped performance

[fadern]

Hi,
I've been running a WG tunnel to Mullvad for over a year now without any problems. Great speed but it's capped to 70MB/s.
Now I noticed that I only get up to around 10MB/s and I see alot of packet loss.
I have followed the guides provided by opnsense.
https://docs.opnsense.org/manual/how-tos/wireguard-client-mullvad.html
https://docs.opnsense.org/manual/how-tos/wireguard-selective-routing.html

I have even tried to create a new tunnel to ProtonVPN and I see the same issues with that tunnel. So I guess that the problem is somewhere in my setup...

What could be wrong and how do I troubleshoot this?

[DEC670airp414user]

what processor is in your router?

what MTU are you using and have tried

[fadern]

Hi!
I use MTU 1420, set in Wireguard > Instances. I have tried 1280 but the packet loss did still exist. https://mullvad.net/en/help/wireguard-and-mullvad-vpn
Max mss 1380, set in Normalization. I have tried to disable this but it doesn't help.
CPU = i7-8550U CPU @ 1.80GHz (4 cores, 4 threads)
When I utilize the Mullvad tunnel I also get packet loss at the Proton tunnel even when it is not used.
Please see the attached screenshots.

[DEC670airp414user]

have you added the MTU change to the interface for each tunnel to see if that helped?
how many different locations have you tried.   and are they all the same

verified your wan interface also is not the same loss?

[fadern]

Now I have tested with MTU 1412 and it doesn't get any better. I even uninstalled the intel-ipsec-mb package but it didn't matter. Have tried both Mullvad and Proton, two different companies and servers.
Speedtests that are going outside the tunnels gives me the expected speed and no package loss at the wan interface.

[fadern]

After a few reboots and uninstallation of the intel-ipsec-mb package and its tunabled the speeds are back... All other settings are the same.
Tanks for your time @DEC670airp414user