The HTC One X is a damn good phone. Unfortunately, the One X's overall quality seems not to have been incorporated into HTC's quality control - already there have been reports of bothersome game lag, and now XDA user bigoliver has shed light on an even more grave concern: the WiFi antenna has been acting up on many devices.
XDA also lists countless other videos to prove the point
As demonstrated in the video, finding out whether your One X is affected is simple:
Gently squeeze the side back of your phone, between the camera lens and the volume buttons, if your WIFI signal strength improves only to drop back down when you stop squeezing then you have this seemingly common fault.