Am using raspberry pi 4 2GB with raspbian os for the last 3.5 months. everything was going well. From last week wifi is not get connecting. my pi can able to detect wifi but it's not connecting with the network. But when I use an external wifi dongle both the internal and external wifi is getting connected. But the internal wifi connection is very very slow compared to its previous performance. I inquired about this with my friends who are all using raspberry pi 4 everyone's pi is working fine, but one guy is having the same issue. While using 3b+ also met with this same issue.
I want to understand why it not and what's the problem, if we can solve the problem means what will be the solution. am having around 10 raspberry pi 4 but only on one raspberry pi am having the issue. if the internal wifi module is faulted means how it can able to connect when I put an external dongle. it kind of confusing.
And one more thing if its off topic means suggest to me where I need to post this issue