Lexmark CS510de not printing 100% scale

Hello,

I've had my Lexmark CS510de for many years but only recently have I noticed that it's not printing at 100% scale. I printed a test PDF with a ruler measurements and it appears to be printing at about 96.7% scale.

I've had a look through all the settings but can't find anything that might be responsible for this. Does anyone have any ideas I can try to get it to print 100%?

Thanks!