RBR50 Router going offline after almost 2 years

You aen't by any chance working remotely and connecting to work through a vpn are you?

The reason I ask is because I started experiencing this exact issue about a month or so ago and was completely perplexed as to why my router kept losing it's internet connection.  I updated my firmware and power cycled everything and it worked for a bit and I thought I was in the clear.  Then i started getting the same thing happening again and again.  I just so happend to notice one day that I always seemd to be remoted in to my work laptop when this happened so I started researching and I found out about an issue with a recent update to Pulse Secure which caused an issue with the Juniper Network Service.  Here's what they said on the website:

"This issue is caused due to an interoperability with the Juniper Network Service which binds to physical adapters when Pulse Desktop Client is installed."

So I followed the instructions and disabled the Juniper Network Services option on my physical and virtual adapters (you actually have to connect to the VPN to see and modify the virtual adapter) and that was the ticket.  I haven't had a problem since

Here's the link to the PulseSecure KB that I used

If this is your problem than the advice on that link should fix you right up.  If not then I hope you find your issue and I hope that this info maybe helps someone else who's experiencing this problem and doesn't have an idea what's happening