I've been using my trio of XE5300s in AP mode for a solid year. 2/3 units are connected via ethernet. Never had any issues with them.

Recently I decided to try using them as a router. Everything was going great and I was able to hit my max rated U/D speeds on all all devices both wired and wireless... until I tried starting a torrent. Suddenly, I noticed the network would drop entirely and my 'main' Deco unit would reboot (ethernet/wifi drops out and the light on the device turns red for a while), sometimes several times in a 10 minute span. When it isn't rebooting, my speeds drop from over 350/350 Mbps up and down to around ~80Mpbs. Everything returns to normal once the torrenting is stopped as measured via Speedtest.net.

Same thing happens with Usenet. Speeds plummet until the download is stopped.

I have QOS disabled on the Deco units, and the firmware is up to date. I'm not sure what else to check. In case it matters, the device running the P2P clients is wired to the main unit. I never had this problem with my old Ubiquiti Edgerouter X and if that thing could handle the connections, so should these.