R7000 2.4ghz not working but 5ghz is fine

So, after I made the changes to the router settings described in my previous post, the the 2.4Ghz remained perfectly reliable and ran without incident for 30 hours. However, shortly after I made the changes, I noticed that the my netflix was buffering a lot more than usual. I have a 50 megabit ISP that can peak at 70 megabits so I knew something was up. I used speedtest - ran it about 30 times from two different PCs on my network (using Ethernet connection) and on several wifi devices connected via 2.4 and 5Ghz. If you can believe, the wireless results were between 45 and 50Mbts on 5Ghz and about 20Mbts on 2.4, which is expected. However, my ethernet connections all tested at 0.2 to 1.4Mbts - WAYYYYY slower than it should be. I bypassed the router and went direct into modem - got to 48Mbits minimum speed and bursted well of 50. Ran about 20 tests over an hour and tried hitting different servers: exerienced some variability but very little and all within expectation. I connected router (without rebooting) and went back down to about .02Megabits. OUCH. Rebooted router and modem. Ran tests again. Exact same. I undid the settings I changed (described in last post), rebooted router and modem. I recovered my performance in LAN but the 2.4Ghz modem fell off again. I called support, we spent 2 hours running every conceivable test and, in the end, they decided that there was a problem with the router. Durring this period, my first teir tech was talking with his backup support (teir 2) and he told me that this router might suffer from being made with parts that did not meet design specifications. He offered RMA. I went to Best Buy and bought another identical router (original was purchased from Amazon). Plugged it in yesterday, configured it exactly as I had originally with the first router (nothing fancy), ran two hours of tests. It was perfectly stable and FAST and has been running without issue for about 40 hours now. The model numbersare identical on the two routers but one I had all the trouble with has a serial number starting 44475B and the new one from Best buy (and that works perfectly) is 44475C, suggesting that it was made at a later date and therefore might benefit from containing different components or at least same components from a different batch. Therefore, I conclude that what the support rep told me is likely true: some of these models include parts that function but which do not meet design specs and, the result of this is that the router manifests easily producable and unexpected issues not usually identifiable until the modem is deployed and the issues cause noticible trouble. Lots of people might not have even bothered to test the speed of their modem and, if they had, they might have assumed it was the ISP. Now that I have a fully functional version of this router I am both happy and impressed. Too bad I had to outlay so much more money for the replacement and also had to spend about 40 hours over 9 days and talk to four different support reps to learn the truth of the matter. On the plus side, I found netgear support easy to access and seemed committed to heping me resolve the issue.