Conflicting IP addresses on your LAN perhaps?
Can you run a long term ping from your EdgeRouter and see if it has issues too or if it is just things behind it?
I'm sorry, what do you mean with conflicting IP addresses? I've made sure to run the ISP router -> EdgeRouter connection on a different Subnet, and the EdgeRouter is the only device connected to the ISP router.
I've run a ping test for a while from the EdgeRouter, but I can't seem to be able to replicate my issues during a ping test unfortunatly. It's really quite puzzeling me
if two devices in the same LAN have the same IP address, the sending host or switch gets confused and tries to sent packets to the wrong receiving device. this can cause long periods where devices seem to "drop off" the network, or only get some of the packets they are expecting.
if you have no issues with device-to- device connectivity (e.g. large, long lived files transfers between your PCs are fine), then its likely not the problem.
Conflicting IPs on your LAN can cause things to stop working but fix itself fast enough you don’t catch what is going on. I mention it because it just happened to me. I had a static IP set but didn’t realize it was within my DHCP range.
However I was able to eventually catch it with a long running ping test.
It could be something silly, like DNS on the edgerouterx still being set to the old ISP's.
It could be that the ISP is still stabilising your line.
It could be that whenever the connection drops and reconnects upstream from the ERX, the ERX takes a few minutes to re-establish (or if your provider does not give you a static IP, recover from the external IP change).
Make sure you haven't done something crazy like set the external port of the ERX to the same IP as the ISP equipment.
If you don't have anything very complex, you could nuke the ERX and restart everything.
Or if your ISP runs on PPPOE, you could try bypassing the ISP router. (And also, if you're using pppoe, make sure your MTU isn't too high)
is your ISP double NATing you? specifcally, are they providing a public IP address to your EdgeRouter? ISPs will often provide a residential router/modem combo and their router will distribute a private IP to your router - a double NAT. double NAT is usually not a huge issue, but its not nice to live behind one. if the ISP confirms that their equipment is bridging (and not routing), then the double NAT issue goes away.
all of the symptoms you describe sound like intermittent packet loss and there are lots of possible reasons for this including poor signalling from your ISP and misconfigured routers (possibly your ISP customer premesis equipment)
as long as your have verified good LAN cabling, including the ISP CPE to your router (you indicated a switch to GigE+ speeds - that needs good copper), the fact that you get this possible packet loss from devices behind your router but not between your router and the ISP CPE may mean your router and the ISP CPE are not playing well together due to double NAT.
hope that helps.