Create complex repeat grids and layouts

I need a repeating product grid for a seasonal catalog that aligns to the existing 8-column layout and preserves exact 4mm gutters. Produce a sheet of 48 artboard-ready tiles arranged 6 across by 8 down, with every tile constrained to 120mm square and holding live type that remains editable. Check for any misaligned anchors, export-ready slices, and name layers so the production printer can impose without manual fixes.

Before I hand this grid to marketing for copy insertion, make approving it obvious: surface the master spacing and tile size in a single top-left note, add an alternate two-column variant so approvers can imagine copy flow, mark any tiles that use non-outlined fonts, and flag images that fall outside safe-action margins.

I just placed 48 product tiles into the master grid for the summer catalog and a set of tiles appears visually tighter even though the math should match. Priya in marketing will review tomorrow and I can’t explain why. I’m worried it’s either hidden transforms on a symbol instance or inconsistent stroke alignment. What is the most likely diagnosis and the fastest sequence to prove it and fix it before I send the PDF?

Every quarter I rebuild repeat grids from scratch because past sheets arrive with inconsistent gutters, unlabeled slices, or embedded fonts that stop prepress. I lose hours cleaning and risk missed deadlines. What three habits should I change in how I set up the master file, name layers, and prepare export to prevent this rework across future catalogs?