Thanks for your help.
I agree and to narrow it down even more I wired one directly to the switch nearest the server.
Some examples of bad frames (Cam1_3.jpg is a normal frame for comparison):
https://goo.gl/hyk9ukOn Camera 2 I noticed that the problem occurs only in night mode and then I noticed it going away after a while, when we turn off the light string. The light string doesn't have a switching power supply and it doesn't blink so I doubt it's generating too much noise.
On the images the glitch always occurs over the length of the lights, maybe those bright white dots are making a bug surface somewhere...
That's the one I wired to the switch before noticing the weird places the glitch was occurring.
On Camera 1 the glitch occurs both in day and night mode but at different places depending on lighting conditions, still on bright well defined spots.
I lowered the angle of this camera slightly, if the glitch moves with the content of the image, external interference can be ruled out entirely.
You'll notice that on the OP's images the glitch also occurs on a bright blob, I think that narrows it down a notch. ^^
Time to wait and see ^^
Edit1:
I added 2 images "Cam2_moved_x.jpg" showing the glitch tracking the same spot it did before, now I'm lowering the quality to see if it changes anything.
Edit2:
After setting quality from very high to medium for an afternoon, no false positive.
I'm now trying very high quality but lowering the fps from 20 to 15.
Edit3:
15 fps still glitching, lowering to 7.
Final Edit:
After much testing on both cameras, here are my results:
-It's corruption and it occurs around bright parts of the image. (Changing the angle of the camera and maintaining lighting condition makes the error move with the part of the image causing it.)
-It occurs at any framerate, and any quality except medium.
-I tested:
-All day/night modes
-All framerates including auto
-All quality settings
-Wireless
-Wired
-On 2 cameras