Check out the last line of this warning sign photographed by Barry L.
They meant to write "stay away from the partition when it's moving" or something along those lines. It's another case of not-quite-right construction that results in giggles. "While" is a conjunction (and sometimes a noun) that means, essentially, "at the same time" (and a few other things).
The second part of the sentence needs a subject, or the "in motion" will refer back to the subject in the first part.
What's the fix? Always read out loud. The ear catches these things better than the eye. And, choose the simplest way to say something, rather than the most official sounding. "Students: Stay away from the partition when it's moving."