This one's a little weird and maybe it's just me being paranoid. Not a big deal if I don't solve it unless things get worse but happy to hear some suggestions.

So, I have a camera on my garage pointing at the house for security. Initially I connected it by wi-fi but the connection was unreliable.'To fix this I used a set of powerline adapters and because I had it laying around I set up an old tp-link modem/router as a wireless access point & switch then ran an ethernet cable from that to the camera. This is now very reliable. I also use the shed wifi connection to a smart switch to let me open the garage door - also very reliable.

So that's the setup, here's the issue. Every now and again when I get on the internet after work a lot of sites fail to connect or there's a big delay before they work. Sites like youtube, stuff, this forum, all give me issues.
Just peak demand and congestion maybe I thought to start with, but it's bad even considering that. I have 100mb fibre and it's generally very fast any time of the day.

Here's where the paranoia kicks in, one time when it was particularly bad I logged onto my router and rebooted it to see if that would help. It fixed the problems immediately, in fact too fast because the internet didn't drop. I rebooted the wrong router by mistake (the one in the shed), and because all it does it extend wifi and an ethernet connection into my shed it shouldn't have worked. So now I'm wondering if someone is periodically hacking into my shed wifi or the stream from the camera or something, or is it possible the TP-Link is having a breakdown or the two routers are not getting along? The shed router is configured as an access point with the wizard and DHCP is off. It works fine most of the time.

Any Ideas welcome, my main router is the one supplied by chorus and has been remarkably stable for a freebie. I think I've rebooted it 2 or 3 times in the last 2 years.