Hi @svgshreyas
Try using the phone's WiFi as close as possible to the network router i.e. <10cm and check if there is a stable connection.
If there is, then it may be an antenna problem in the phone, loose or faulty antenna perhaps.
Here's an image from this teardown [https://www.youtube.com/watch?v=j0vmTmktXVg|video] that shows both ends of the antenna and where they're connected to on the boards.
[image|3055395]
9click on image)