2.4ghz Suddenly Dropped, Help Needed

[#1]

I have 45mb speed DL and 5.8 UL.

10 devices running mostly on router, 2 PS4's running via lan with 3 Powerline Adapters,  4 IPhones running 5ghz, 2 laptops running 2.4ghz.

Asus RT-N56U router attached to BT Supplied Modem.

I have always got 42+mb for years on wifi 2.4ghz & 5ghz and same on lan, until 2 days ago, I suddenly got Kbps on 2.4ghz and done diagnostics and found everything else working fine as usual.

The router and modem have never been moved and the channel has always been on 13 as my neighbours are on default 1/6/11, Never had a issue got full speeds.

I also used the 5ghz capable devices on 2.4ghz and speeds are low.

Ive doubled checked neighbours wifi using software and no one is using channel 13 and all routers are showing up as ISP supplied and probably on Auto wifi selection.

I then thought its the 2.4ghz Antenna on Asus, so decided to swap it with Plusnet Hub one.

Unfortunately that did the same above.

Sometimes the speedtest goes all the way to 43mb and them drops dramatically, and today it's been going to 20-30mb,  

Any help would be appreciated.

Thanks in advance 

[#2]

Moderators Note

This topic has been moved from Fibre to My Router

[#3]

Hi @Faizan786, I'm sorry to hear that you are having issues.

Just to confirm, the 5GHz wireless and wired connection still working as expected?

Have you recently added any new devices or changed anything else in the property recently?

[#4]

Yes, the 5ghz and wired lan work to the max.

I have been using same devices for 3 years +, and never moved router and modem either.

This problem occurred suddenly on friday and has stayed like it since.

Here are 2 speedtests and you can see it fluctuates 

Then it works like treat like usual

[#5]

Thanks for confirming @Faizan786.

Due to the fact that you have ruled out the router and the broadband connection into the property causing the issue, it certainly does sound like wireless interference. Although your router is on a different channel to your neighbours, there is likely still interference on the 2.4GHz coming from somewhere.

To be honest if nothing has changed inside your property I'm not too sure what to suggest, but if the issue continues it might be worth looking into a WiFi booster to boost the signal you are getting.