Even with latest firmware, I still have a very buggy C4000. And some people also experienced problems with it too. Unfortunately, many don't get any solution.

Surely, customers need new firmware to fix the problems.

Some even try not to upgrade firmware as it gives more problems.

I would like to mention my problems:

1. 2.4GHz and 5GHz signals gone. And appears warning: "the 5GHz network is unavailable due to restrictions in your region/country"

  The only way to turn on 2.4GHz, when the warning appears, is to hard reset and disable all the 5GHz, restart, and cross ur fingers.

2. When I pull WAN cable and connect again, 2.4GHz gone and needs router restart. When I changed 2.4GHz settings like Beacon timing, the warning appears and I cant do anything.

3. USB drive connected to usb 3.0 not stable. Sometimes the device can not reading. Firmware said the USB problem is fixed, but not in my experienced.

4. I am too lazy to test the other features of this quad core router as I am sure more problems will come. Basic usages of the router are already buggy, I am sure advanced usage would be more buggy.

Do I regret buying cheap quad-core router that is buggy and unstable?

Yes, I would not make use of this quad core because of the bug, it is much better just to buy dual core router that is not buggy.

I will not make buying decision based on the hardware alone. 

Please, help customers who already put their faith in buying your products by providing us with good firmware fixes.

Thank you.