Intermittent Connection Issues Via WiFi (Ethernet is fine)

[reinhard24]

Good day, this is my first time posting so I hope I've posted this in the right thread. My office currently has an AiMesh setup consisting of an RT-AC88U as the primary router, as well as another RT-AC88U and an RT-AC66U B1 as nodes. Previously, we had no major issues when connecting to the internet, however since last week lately we seem to have encountered intermittent connection issues when accessing the internet. For better understanding, I have also attached a network diagram of our office. I hope its acceptable since its my first time making one (first job as well). Anyways, some key takeaways Ive found:
1. When using ethernet, laptops have no issues connecting to the internet and local resources (servers and printers)
2. When using wifi, laptops have no issues connecting to local resources (EDIT: Devices seem to have some RTO when connecting to local resources, but less when compared to connecting to the internet: about 10s RTO replies for every 5 minutes)
3. However, when using wifi, laptops have issues connecting to the internet (30-45s of RTO every 5 minutes)
4. No issues when connecting my laptop directly to the ISP router
5. Using the network analysis feature from the router, it shows no response from google during the same time that there is no response when pinging via my laptop (have attached a screenshot as well).
6. This could be the issue however I dont want to solely blame this: Apparently, another admin had set AiProtection on for the first time last week. However, after disabling this, the issue still persists.

Steps I have taken:
1. Reboot the routers via the web interface
2. Manually shutdown, waited a minute, then manually turn on the routers
3. Disconnected and reconnected the ethernet cables connected to the router (using only ports 1-4).
4. Disabled AiProtection and Parental Control

I am no networking expert, but I would like to ask some clarifying questions:
1. Is this a network loop? Personally I dont think so since that should affect devices connected to the ethernet as well
2. Could this be a firewall issue? I disabled AiProtection and parental control however the firewall feature is currently still turned on,since I think its a bad idea to disable it, since we would have even less protection as well.
3. I would prefer a hard reset to be my very last option, since we have no saved config files from when the routers were working well (Lesson learned). Any other ideas?

Thanks

 

[ColinTaylor]

Look for clues in the primary router's System Log.