GenerateBlocks is producing a page specific css file for each page, that’s where the padding for the container is declared. Using W3 Total Cache with a “push” style CDN, that file has to be pushed manually to the CDN each time it’s edited… and only as part of the “custom files” upload, which is quite slow as it captures a lot of files.
Not a bug, exactly, but I’d say an incompatibility between using generateblocks and using push style CDN with W3TC.
Anyway – thanks for the help. We can call this solved.