What were you filming, an image projected onto a screen?
This looks like the moire effect:
https://en.m.wikipedia.org/wiki/Moir%C3%A9_patternYour best bet is to ensure that your camera's sensor's pixels are picking up multiple projector pixels (it does reduce your effective resolution though) or that multiple camera pixels pick up a single projector pixels (you may not have enough resolution to do this).
You can see this kind of thing in the wild if you look back at 2010-era live concerts with video walls. As the camera zooms in on the singer there a spot where the moire pattern is really bad and then it goes away as the ratio of camera pixels to LED wall pixels changes.
Edit: Found a good example here:
(Start at 45:51. The embed on this forum breaks the timestamp in the link.) Make sure you watch fullscreen and keep an eye on the LED wall as the camera zooms.