Canon Pixma Pro 1000 misalignment of grey paper guides

[RichardW]

Printer about 5000 prints in using Fotospeed NSTBW cotton 315gsm, since a year ago, CS2, with correct colour profile from Fotospeed. However when printing A4 the white margins are misaligned despite the guide set central to the edges. To have equal white margins paper is pushed to the left about 2mm resulting in a perfect print. A3 has no issues but A2 has to be pushed to the left 2mm to get good margins. What is worn? The central roller is clean and the print head has been aligned. Canon say it's the thickness of the paper but the distributer says not