GXV3610_HD resetting to 640x480


Hello, my GXV3610_HD started to reset itself to 640x480 almost every night. Otherwise it works well but this is a serious issue since the surveillance software loses connection to the camera when this happens.
I tried to reset to factory settings and update to the latest firmware but the resets still occur.
What can I do? There’s no warranty anymore as the camera is almost 3 years old.