@Bennett 

As for the wireless unstable connection, we need do further analysis.

1. The led status of TD-W8961N when you lost wireless connections. 

2. Can you see the wireless network name at that time? Or it is still connected but no internet access?

3. Try to change the wireless settings to improve the wireless performance, including wireless channel and channel width. 

4. Besides, you can assign a static IP for the wireless devices to give it a shot. 

Good day. 

@Kevin_Z  Hi Kev.

1. LED status is ordinary and shows everything fine.

five lamps are on. wifi , LAN and internet blink.

2. yes , i can see wireless name , i am connected to wifi but no internet access.  its no difference if your device is android or IOS or windows. it happens to all wifi devices.

3. i am a professional.  its my job to solve this kind of problems. simple things such as channel changing, bandwidth changing, changing between AES/TKIP or etc are already tested. i think its a hardware problem such as a stack over flow or catch problem.

4. changing between static and dynamic IP makes no advantages. its tried and no use to do that. 

are you working for TP_LINK Co?

@Bennett 

If it's  a wifi connected device there is an issue with hidden networks, so if the SSID is turned off on the router the phone/tab/chromebook may struggle to connect or remain connected, this is especially bad on the 5ghz band,

Solution is when setting up the device to connect to the router to select advanced settings on the device wishing to connect after entering username encyption and password settings, this drops down to be able to select Hidden Network then save, that's supposed to sort it but doesn't always,

Short version

If you have the router set to not broadcast it's wifi ID's there is the possibility of connection problems, it's something to do with Google updating their security settings and possible Apple has done the same thing, hth.

@Hannibal_Lack

Hi

SSID is not hidden.