Resilient (Ethernet+Wifi) Router->Router Connection

Question

I have a router, connected to my modem, downstairs in my house.

This is connected to a HomePlug, the other side of which connects to a second router upstairs. This allows me the lower latency and higher throughput of an Ethernet connection for computers near the upstairs router and better WiFi coverage upstairs.

This mostly works fine, although sometimes the HomePlug connection drops for some seconds up to a minute. It usually fixes itself without intervention or can be fixed immediately by switching off and on the HomePlug again. I have tried a couple of different home plugs and they all have this issue. I read it may be to do with Power Saving so run a scheduled task to ping my downstairs router every minute to ensure traffic is always going through the line but this didn't help.

This is highly annoying when watching a stream, or in the middle of an SSH session etc.

Is there a way to set my upstairs router to use the home plug if it is working, but fall back to a wifi connection to the downstairs router for the small periods of time that the homeplug disconnects?

Failing that, has anyone experienced this Home Plug issue and know of a model of Home Plug that doesn't have this issue?

Can add the models etc. if required but not sure if its relevant - Happy to buy new hardware if someone can give me a suggestion that it will work in this manner.