Sounds like you got a refurbished router for your $25.00. How old is it, if I may ask? If it's more that three years old and a refurb. My feeling is, it is on the way to dying.
I had a client who hired me after the previous Tech stopped responding for calls to service. Meaning I inherited whatever he did. For months I chased a ghost problem of the internet dropping connection. One day I was in the closet where all the network hardware was mounted and installed and I decided to re-route all the cabling and it was during this process that I noticed that the wireless router was using a power adapter that was not "Linksys". I had the same router at my home, so I knew it was oddball. No bid deal, right. But something made me dig around and check things out and long story short the router wanted 12 volts DC and this non-Linksys power adapter was delivering 11 volts DC as per it's specs written right on the plastic of the adapter.
Lesson: Don't assume it's getting the right voltage. ALWAYS check.
Plus even if you have the right adapter, it could still be bad, meaning rated for 12 VDC and delivering 10.5 instead.