Low Download on MT3000(BerylAX) Home Router

Hello together,

i hope someone could give me a good hint. First my setup:

Internetspeed without any routers inbetween;
download 250 Mbps
upload 50 Mbps

Home Router MT3000 (Latest Firmware)
Connected via WPN cable to ISP Router
Zerotier + Wireguard Server
Download: 50 Mbps
Upload 40 Mpbs

Travel Router AXT1800 (Latest Firmware)
Connected to Home Router via WireGuard Client + Zerotier
Download 20 mbps
Upload; 20 Mbs

I used this setup 2 months ago, before upgrading to the newest firmware and i didnt had any issues. I think the problem is located on the Beryl 3000 since even when i reset the device or switched between multiple firmwares i couldnt get downloadspeeds faster than 50mbps.

My Upload is stable but my download speed is horrible.

Am i missing something or doing something wrong?

How about the WireGuard speed if disable the Zerotier?

What firmware version do better than the latest (4.6.4 or 4.7.0?) ?