No clue. What "State Code" are you seeing at the top of the System Status page (in the System Summary box)?
What modem are you using? HT2000W? HT1100? HT1000? HN9000S?
Also, if using WiFi, try connecting directly with a LAN cable to see if that alleviates the slow internet and buffering. That might, at least, rule out the router as a cause of the speed/buffering issue.
Well, with regard to the state code, you'll see it in the red box in the picture below. If everything's okay, it will show zeros, like mine is.
When you ran the speed test with the laptop, was it the only thing connected, and was it connected via LAN cable? If you are able, it would be good to try a few speed tests that way, with the laptop directly connected using a LAN cable. While you are doing this test, make sure nothing else is connected. You can temporarily turn off the WiFi radios in the modem through the WiFi section of the System Control Center. The password is admin . Just uncheck the boxes for the 2.4Ghz and 5Ghz radios, and you have to do each radio separately, or it won't save. The 2.4Ghz radio (both boxes), then save, then the 2.4Ghz guest (both boxes), then save, then so on for for the other two.
The reason I suggest trying a few speed tests this way is that it excludes the Wifi, which has a lot of variables that can cause issues, and it excludes any of your other devices stealing speed from the one you're testing with.
Also, you should perform the tests at the site testmy.net, and it's best to create an account and run the tests while signed into that account so the tests are saved. And, use the 25MB manual download test.
I can't get the System Control Center link to post correctly for some reason, but I think you already know how to get there. If not, you can type 192.168.0.1 into the address bar of your browser and hit enter.
Please copy/paste your testmy.net test results URL into a reply. That's the URL in the address box when you click on Results while signed in to testmy.net. This way the Community reps can take a look at your speeds.
It will look like the following, but with your testmy.net user name where it indicates such... http://testmy.net/quickstats/[yourusername]
Also, the System Control Center may look different because of your browser. To get to the System Status page at the SCC you have to click on "System Status" at the top of the page.