I've told this before, but it is still a good story.

I used to sell office equipment for a Xerox agency.  Local service tech related a problem he was having and not good solution.  Customer had a Xerox 645 word processor.  This was a $4000 machine 20 years ago. (yes, those numbers are correct)

Customer had a typewriter that was inserting random characters in documents.  Tech replaced the keyboard, the CPU, cables, any and everything he could think of.  Finally one day he told the secretary he was just going to set and watch her work and see if he could find a pattern.

He told me he found the problem, but was at a loss to fix it.  Seems the lady was ... amply endowed.  When she turned around she brushed the desk with her umm ... massive attributes and the typewriter just did what it was supposed to do when a key was pushed.