What Wireguard MTU do you use? Is any Keep-alive set? I would try to lower it to 1280 and go up till you find the max speed.
Also which vpn provider is it?
I use Mullvad for example, but as many vpn do they share the same ip with other users very similar like cgnats, so that opens the chance someone could have been doing naughty things and the ip is under attack or throttled by the big cdns: akamai, amazon aws, Cloudflare etcetera.
Even a simple word which was in their blacklist could temporary blacklist or throttle your vpn ip, often it gets used as a service within their cloud/cdn environment.
Have you tried changing to a other vpn connection which seem less populated? (Not the first available one in the row?).
I did the test with 3 different providers.
Nordvpn
Surfshark
PrivateVPN
Always different servers. Tested multiple times.
No one else has access to the network.
Nothing was changed in the entire network or PC or cell phones.
So that's more than strange with the device. I have now tested 4.6.2 and 24 each.
3 Different VPN providers and numerous servers. Always clean install and redo everything.
For whatever reason, the VPN keeps getting slow and slow and slow. From 260 down to 5 or 10 mbps. Only restarting the device brings improvement.
Counter-tested with an Asus AX86U, same servers and same settings as the Flint. No problems running through!
I need some more info, like what is your current connection?
Like is it mobile based, satalite, fiber?
my gut feeling says it might be the mtu setting on the vpn client and depending what type of internet is used you may want to make it very low and test or even increase, but never go beyond 1500 mtu, 1500 is often the max, and 1508 maybe only for a added vlan packet overhead but nothing more.
it can also be the gl-inet router that just use a high mtu and the isp throttle that due to big jumbo packets, mine does that on 1500 mtu, but when it is about mobile connections you often see people going much lower, its a different landscape and policies they use there, ive seen marcfifty once mentioning in his videos he went around 750 mtu so yeah, try incrementing from that mtu and see 
I have this problem in other devices with slow CPUs, but not on Flint 2.
If this is the case, you can monitor the CPU Load on the Admin Panel --> System --> Overview:
Are you running Adguard Home with multiple filters?
If yes, make sure the filters are really necessary because I noticed many people using filter like "HaGeZi Multi PRO and Multi PRO++ and Multi ULTIMATE" all together, while Multi ULTIMATE already have all filters from Multi Pro and Multi Po++
The connection is via Starlink. Different MTU values were also tested on both devices (Flint 2 and AX86U) the Flint became slower and slower and slower as the hours passed.
Both routers were always set up almost identically and tested independently one after the other.
No Adguard or anything else that would burden the system was activated
Adguard is not activated because I'm looking for errors and can't find it at all.
Maybe StarLink is just throttling your connection? Or the connection itself isn't good.
As I wrote before, somewhere in your threads: Try TCP VPN instead of UDP VPN.
2 Likes
400Mbps is not a typical speed for Starlink.
Depending of your plan, it's normal to see 5-50Mbps (Download) and 2-10Mbps (Upload).
1 Like
measured at different times with different speed test providers.
over 250 is standard for us. All neighbors have these speeds and use one VPN
and it only throttles the speed on the flint 2 and on the Asus AX86u it doesn't matter ???? Don't think it's throttling Starlink
There is no TCP with Wireguard
I believe admon means OpenVPN TCP.
2 Likes
Ofc. But I wrote it so often that I don't think @Funnyland is really interested in troubleshooting at all.
Btw: „Verlust“ in your first screenshot already shows that UDP is a bad choice.
1 Like
Hello, I was looking for a clue yesterday and did a little searching. Here in Germany 250 mbps are normal Starlink speeds.
I only use Wireguard and there is no TCP there.
TCP is only used with OpenVPN, which has of course also been tested and is extremely slow and slows down the router unnecessarily. Why not use the faster, more system-friendly one 
Clean install on 4.6.3 opt 24 was of course also tried but with the same problem as before.
The speed should be that one from the Starling site I showed to you before.
What is your Starling Plan? Standard? Mobile?
Are you setting the wireguard on the router or on your PC/Smartphone?
How did you set the wireguard for NordVPN?
This is not a standard protocol for them.
The screenshot above tells us that you experience some package loss which is deadly for all VPN connections.
So you might need to find a way to reduce the loss. How this can be achieved is something you will need to try by your own because reasons can be very different. MTU, cable, connection itself … many reasons.
OpenVPN TCP shouldn‘t be way slower. 190 Mbps are possible - but speed will drop due to package loss until it is more or less stable.
So your main issue is the package loss.
Which screenshot shows this?
The first speedtest shows 1,7% loss.