AC 10: Grid prints on Layout even when turned off

[SeaGeoff]

I have a weird problem. My Layout grid is printing even though it is turned off and does not appear in the layout window. I've only discovered it in one file so far, others appear unaffected. Anyone else encounter this? TIA.

[SeaGeoff]

Here's the same layout printed to PDF. Same thing happens if it's printed.

[TomWaltz]

I've seen it randomly on different layouts. Usually just reprinting makes it go away.