This seems like such a petty annoyance, but it's driving me (and some of my students) insane...
I teach a computer applications course at a community college and use some auto-grading software for students to submit work. The work is done in the Excel application (not a simulation). One of the tasks is to set an Excel spreadsheet column width to a specific size. One such size is 15.86, another is 14.11, and so on. Students have reported that they apply these settings, but when they redisplay the column width, the settings have changed...usually by 3/100, so 15.86 becomes 15.89, 14.11 becomes 14.14, and so on. Sometimes the sizes change up, and sometimes down. I can replicate this on my own two copies of Office (one on my desktop, one on my laptop).
I know in the real world, people rarely need such precise column widths and instead probably just auto-fit to the widest entry, but a) students are getting marked wrong, and b) it's driving me nuts that I can't trace the source of the error. I get similar behavior whether I access the column width dialog by right-clicking the column, or by using the ribbon (Format > Column Width).