For the past few weeks I have been having an issue with Hardware NAT, which my router supports, not working on OpenWRT 18.06.8, I tried downgrading the firmware to as far as 18.06.2, where it worked for a while, then when I tested it a few hours later, the CPU load goes up to 20-25% when I ran a speedtest, showing that Hardware NAT was clearly not working. I assumed it was NAT6 since I had heard that it was incompatible with Hardware NAT, or maybe it was WireGuard VPN, since I had heard the same thing about that. and so I flashed again 18.06.8, this time I did not install NAT6 or WireGuard VPN on the router, because I thought one of those was the culprit. Initially when I flashed 18.06.8, reinstalled all my packages except for those two, and restored my config, and ran a speedtest I noticed the CPU was not being used to forward packets and Hardware NAT was working just as expected. However now, a few hours after that, I tested again with a speedtest and the CPU load goes back up to 20-25% when I run a speedtest? Why is this? How come Hardware NAT works and then few hours later stops working, what can I do to get it to use Hardware NAT once and for all and make it such that Hardware NAT is the only option, and it can't fall back to Software NAT under any circumstance?
Edit: Whenever I reboot my router and run a speedtest, my CPU usage stays at 1-2% like I expect, and it uses Hardware NAT, but then I got up, came back 5 minutes later and ran another speedtest, and it goes back to using software NAT and processing the packets through the CPU, why?
Edit 2: I noticed that when I run a speedtest on my computer, the CPU is used, but when I run a speedtest on my phone (which is connected to the Edgerouter's LAN through a Wi-Fi access point) , it seems to use Hardware NAT. But then if I try a few minutes later, the phone uses Software NAT again and the traffic goes through the CPU of the router. Very strange indeed.
Edit 3: It seems that if a connection is open for more than a minute or so, it switches from Hardware NAT to software NAT, also very strange and unexplained behavior.