Please help D'Link DIR-825acg1router problem

[CB40]

Please can anyone assist. I have the above wireless router and after the latest firmware upgrade I am having major problems with wireless connections to my Samsung S9 and an HP 8600 printer.
The 2.4Ghz & 5Ghz keeps dropping on the phone and the printer struggles to connect on 2.4Ghz.
I have noticed on the upgrade there is an address on IPV6 which was never there before the upgrade.
It does not reset the firmware to the previous version after a factory reset.

 

[Rickster]

How is the wireless interference in your area.

Also make sure the Channel for the 2.4 band is not set to anything higher than 12

 

[CB40]

How is the wireless interference in your area.

Also make sure the Channel for the 2.4 band is not set to anything higher than 12

Had no wireless interference as far as I know, the 2.4 band is set to Select Channel Automatically, it was on Auto 1 and I changed it to 6.
Sorry a real noob at this sort of thing so need all the help I can get.

 

[Willy Strong]

Flash previous firmware version again?

 

[CB40]

Flash previous firmware version again?

How do I do that??

 

[Willy Strong]

1. Go to the Dlink website and search your router.
2. Download correct firmware.
3.???
4. Hopefully it's not bricked.
5. Profit.