Do you have any motion interpolation features turned on? Repeating patterns like stripes or grids play havoc with those. If the camera moves approximately the same distance as (or a multiple of) the repetition interval of the pattern, the interpolator is going to have difficulty telling the difference between that and if the camera had moved by a different multiple, or not at all, when trying to draw an in-between frame.
Otherwise it might just be artifacting caused by the compression used on the source video.
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