Hi @u9ci
Try using the phone's WiFi (or BT) as close as possible to your home network router (or BT device) i.e. <10cm and check if it detects the WiFI network (or BT device) and connects and maintains a stable connection or not.
If it does then there may be a problem with the WiFi/BT antenna in the phone. A loose connection or faulty WiFi/BT antenna perhaps.
Below is an image taken from this teardown [https://www.youtube.com/watch?v=OiYMYkOQZqU|video] showing the location of both ends of the antenna cable, where it connects to the boards.
If you determine that the antenna is faulty search online for ''GH81-20151A'' to find antenna suppliers that suit you best.
The same antenna is used in a lot of Samsung models, not just the galaxy A02.
[image|3639592]
(click on image)