MBP looses WiFi after a few hours.

[VideoBeagle]

Computer: Macbook Pro 2.2 GHZ running 10.11.16

I recently changed routers, going from an N router to an AC Router. While the MBP can't do AC, it connects via N and has had a good speed boost.

HOWERVER, after a few hours, the wifi partially stops working. I say partially, because the upload connection isn't affected, only download...it drops from 100Mbps to below 1Mbps. I stay connected to the internet and can still SLOWLY go to web pages etc, but tat's it.

IF I disconnect the wifi, and then try to reconnect, I get a "can't connect" error. Same if the computer goes to sleep, and I try hours later. BUT, if I reboot, everything is fixed instantly.

(top is speed test after reboot, bottom is before)

Connections to other computers on my home network are affected, so it's not about the internet.
Other devices on my network using wifi (iPhone, iPad) do not have this problem and are fine when the MBP is having it's issue.

Given the above, I assume it's something software related, but I don't even know how to start looking for a solution.

Any help?

 

[VideoBeagle]

Additional: Wile it was in the "not working" phase, I plugged it into my ethernet....wouldn't acknowledge that I had done so. No connection.
Restart fixed that as well as the wifi as usual.

 

[VideoBeagle]

This may trigger after 3 hours of active use...but my testing is inconclusive.

 

[VideoBeagle]

Testing on a time element as proven false, so I'm unsure what triggers the bad phase.