This is common issue with the PTZOptics cameras. 

This issue occurs because the anti-flicker setting built into the PTZOptics cameras comes set to be 60hz. This is a feature that is available to combat some of the undesirable effects that can happen from different indoor fluorescent lights. This article goes over the issue a bit more in depth. With this set to be 60hz or 50hz, you get an over compensation of the lighting effect in bright outdoor settings. If you turn this setting to off in the Exposure menu in the OSD, you will get rid of this issue. 

Here is an image of a very dark and cloudy day with the anti flicker set to be 60hz. 

Here is an image of the same camera with the same conditions with the anti flicker set to be off.