Sony PS4 Wi-Fi Keeps Disconnecting and Downloads Fail

I purchased a used Sony PlayStation 4 Fat, and since receiving the device in mid-July, I have been experiencing a serious problem specifically with its Wi-Fi connection. There does not appear to be any general problem with the console, but the wireless internet connection constantly disconnects, and I frequently receive “failed” errors, especially when trying to download content. Since I do not have the option of using a wired internet connection, I am forced to rely on Wi-Fi and therefore cannot use the console properly.

I use Türk Telekom internet in Istanbul, and I have confirmed that the problem does not occur on the other devices in my home. It only occurs on the PlayStation 4. I have tried numerous troubleshooting methods, including changing the network settings, adjusting the modem settings, changing Wi-Fi channels, and other similar solutions, but the problem has not changed. I continue to receive a “failed” warning, particularly during download speed tests, as also shown on the test screen.

I request that Sony provide a clear solution to this Wi-Fi problem even if the console is no longer under warranty. If possible, I would like the device to be technically inspected to determine whether the problem is caused by the console itself, and I request that the issue be resolved through a software or hardware solution without any additional charge. If the problem is resolved, I simply want to be able to use my console normally without further connection issues.