I am curious if there has been a change in any of the recent CC updates that could be affecting transparency flattening and resulting "stitching" effect that happens to raster images that interact with transparent areas. For over a decade, the universal response has been "those won't show up on the print." That seems to have changed in the past 2 months, where I've seen at least 2 instances of the stitched lines making it onto the printing plates and being visible on the final print. In one case, the lines were not presenting on-screen when viewing in Acrobat at all magnifications. Both were output with the standard PDF/X-4 & compatibility Acrobat 7 (PDF1.6). It was exceptionally bad when outputting a linked .eps file containing raster, vector, and bitmap elements from an InDesign template.
This was standard practice for years prior with no issue, so to see 2 instances in the past 2 months has raised some alarm. Are we back to the bad old days of worrying about transparency fractures in print?