EDIT: I re-read the description of the issue and see that there is intermittent islands of stability. Take the following post as just some insight from someone hearing your plight, I'm not sure if I'm hitting the mark or not.
I noticed a shift a few years back (a decade now maybe?) where wifi connections were demarcated as failed to connect or no internet connection on the mere premise that DNS is failing. In testament to this, if I block DNS on my home network that my Meraki Go wifi clients use - they start to complain that the wifi is not working. The reality is, this health check on the mobile is entirely based on "is DNS working?". My android devices will connect in these circumstances, but say "Connected, no internet".
I bring all of this up @IanTerry because this shift in the industry has made it harder for us, remotely, to tell if you are having wifi issues (like interference) or an issue on the wire upstream of the access point. Both of these can cause DNS to fail, and have the wifi marked as no good.
If the changes recommended thus far haven't given much insight - it might be time to check the local status page of the GR10 and get more information. Ideally, we'd want to know:
- Which band you are on during the slowness
- What is channel utilization during the slowness
- What are your speeds directly to the access point
- What are your speeds to the internet
The local status page offers info on your connection, like which band, channel utilization, and also provides a speed test to let you see what your local speeds are. We'd want to pair that with the internet speed test taken immediately after the local status page speed test, as well as identify if there is a channel utilization problem or interfering access points in the area.
Also shout out to @speakerfritz and @TyShawn for jumping in. It takes a village!