Moire Pattern

Not banding or poor printer resolution. I change cartridges when banding occurs. I am using a Canon 6120 Pixma printer. I get unusually good prints until one with lines like roofing shingles comes along. Of all my prints, only two have had the moire pattern. I dont get it unless it shows on my computer screen. What could possibly be wrong with my work flow. Does anyone have an example of this behavior? Thanks
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Christian Amateur Photographer