Question TP-Link WR740N wireless connectivity issues when bluetooth is on in one of connected pcs

Mar 19, 2019
TL;DR - two Lenovo laptops are able to "freeze" the wifi network of my router, one of them just when connected, the other when playing music over bluetooth. This happens only for this single router, and not when connecting them to other alternative routers.

I have a WR740N wifi router, 2.4GHz, channel 6 currently (although tested many others).
It's been working flawlessly for years now, serving multiple devices (several old and not so old pcs, laptops, phones, a printer etc) until recently I bought more recent Lenovo Y700 laptop about a year ago. Whenever I connect to a wifi, in a while the router slows down and eventually stops responding for a moment, then goes back, then slows down and so on.
I've set up a continuous ping (to the router) from my Win-7 running laptop (old Lenovo T520). The ping is constantly ~2ms for hours, but when I turn on the new laptop (Y700), the ping goes down to hundreds then thousands of ms and eventually times out.
I suspected all the possible scenarios with this new laptop but blamed it on the laptop. Until I just got other Lenovo running Win10 too (T540p).
This one works fine, as long as it's not actively using Bluetooth connection.

I have a bluetooth soundbar. The Lenovo T540 connects to the bluetooth soundbar and everything is perfectly fine. As soon as I start playing the music over the bluetooth, the ping goes down on both T540, Y700 and the old one (T520). Actually, every device connected to the router cannot reach the router nor the Internet.
The moment I stop the sound or disconnect bluetooth, all the devices can reach the network again.
Note, for the Y700 this wasn't the case with the bluetooth. Even with disabled bluetooth, it's sole presence in the network caused troubles.

I've tried multiple scenario, summing up:

  1. whenever there's a connectivity trouble, it affects all the devices connected to the wifi, no matter where they physically are located (near or far from the router, near or far from the trouble-causing laptop), therefore I assume it is router issue
  2. Lenovo Y700, Win10 causes trouble randomly (or I didn't spot pattern yet) whenever it connects to the wifi.Not bluetooth related.
  3. Lenovo T540P, Win10 causes trouble whenever it is actively transferring the data (sound) over bluetooth AND is connected to a wifi at the same time. If I disconnect it from the wifi, it doesn't affect the wifi anymore, and doesn't affect the devices connected to the wifi even when they're very close to it. So it doesn't look like a physical interference, rather "logical"?
  4. The old Laptop (Win7, Lenovo T520) never caused any troubles, whether connected to the bluetooth speaker or not (tested hundreds of hours!)
  5. Several phones connected to both bluetooth speaker and the wifi at the same time and played music for hours - never caused any trouble
  6. I've tried setting up the similar network (connected all 3 Lenovo laptops) using different router (although 2.4GHz too, channel 6) and never was able to reproduce the problem. Also connected to a phone hotspot on a regular basis, never had a problem too.
no matter how strange it sound, for me all of it looks like it's to be blamed on the router. Any idea what might be the cause?

I assume the only fix is to change router. First, I'm asking out of curiosity, second - I don't want to end up with a new router and an old problem
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