NextCloudPi - Frequent Connection Timeouts

I’m running NCP on a RPi 4, have ports 80 and 443 port forwarded on my router, but frequently when I try to connect, the connection times out. This makes syncing with the desktop client pretty much impossible, as well as viewing large directories from mobile. If I connect through the LAN address it’s better, but connecting to the WAN is really bad, even when not connected to my home network.

BTW, I would set up dnsmasq but my router won’t let me change the DNS servers…