Progressive moiré is a large wavy pattern, a bit like the Coca-Cola swoosh, prevalent with screen printing. There are a number of elements which can lead to progressive moiré. These include high-tack ink, imbalanced mesh warp and weft stress and count, low fill-rate high-capacity mesh, low mesh tension, improper mesh elongation, retensioning, insufficient off-contact gap, excessive angle and blade pressure, and inadequate press calibration. To identify which are the primary or secondary causes, always print a nine-zone fiducial image.
To fix this issue, you'll need to reduce the stretch on the mesh during the print stroke, reduce ink tack, reduce blade angle and pressure, increase the off-contact gap, never retension screen mesh for halftones, and balance the warp and weft stress and counts.
Source: Joe Clarke