Wifi became weak after dropping phone

Recently I had my housing changed, so I don't know if it affects it but it's not as good as original quality because I bent my previous one on accident. But the wifi was fine until I dropped it from my pocket onto the ground in sitting position, then the wifi stopped functioning normally.

Now the wifi strength is so weak I have to be close to the wifi modem to use it and it will also not receive the best strength..

Is there a possibility for the wifi antenna or other component to become loosened? Sorry I am a total amateur to this, because I find it hardly convincing for the parts to be unsoldered for dropping at this height.

And how do I know which wifi component do I need to test before replacing it?

And I noticed there is a similar post to this which is mainly concerned for iPhone 6, I don't really know if the components are usable for iPhone 6s Plus so I had to post another one.