Internet connection partly down on EdgeRouter X 18.06.4

Hello friends!

I have EdgeRouter X for around 2 years. A couple months ago I started to have an odd symptom of Internet going down, but partly. Some connections like ping and Steam chat continue working, but others like browsers and Discord go down. LuCI, SSH and ping to the router also remain working. I also notice that it happens on some devices like my Main PC and secondary PC, but others like my Ubuntu server and even my Windows VM remain working.

Yes, some times the Main PC (Win10) lose connectivity, but a guest VM on it remain connecting. It's a VMware VM with bridged network adapter.

It took me time to identify it was the router, because I have another odd issue on Main PC that its DNS client is crashing. When it happens, IP connection works, but domains don't resolve anymore. I'm unable to solve this issue, I had already restored a backup made before it started with no luck. I try flush DNS and also nothing. Only solution is rebooting Windows.

Because of this I was just considering it was DNS and didn't try other devices. But, when it's the router, rebooting doesn't solve it. I went to the point of resetting network and uninstalling network driver. I did that some times and it's very stressing. I then tried rebooting the router and Internet came back. After some times, I found out I have another new issue.

When it happens, I test on secondary PC, then just login LuCI and reboot from there, then Internet magically comes back.

But now this week it got worse. Even ping wasn't working and I had to use power cord. I kept ping -t running to keep track of when it restarted, and a couple minutes after it was back it crashed again: ping was still running and I saw when it went offline. Lucky I did another power cord reboot and it's live since.

I haven't upgraded OpenWRT because all those reports of boot loop. Now with this happening, I decided to buy a new ER-X. It's my only router and I've been working from home so I can't stay offline, I found a ER-X (not SFP, mine has SFP but it doesn't work anyway) for R$410 so I just bought it, it will arrive this week.

I thought on buying another model, but Mikrotik is more expensive, and anyway at least having 2 units of the same model it's easier to replicate settings and stuff. I'm also buying a USB-Serial TTL.

My plan is to flash 19.07.7 on the new one and apply all settings to it and place it on production, then try to upgrade old one, maybe reset and reapply settings on it, and keep it as spare. Will use this thread to keep updating the progress.