How recent is your experience with Mikrotik? How old is the hardware you tried out?

What does round filing dmca requests mean?

This. Also, make sure the proxy is proxying websocket traffic as well. I do it with pure nginx like this:

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://192.168.1.100:8123/;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;

        # WebSocket support
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
}