Long ago, in a design center far far away .. (chip design that is. running on Calma and ComputerVision systems driven by a Data General Nova . this is late 80's)
One day we found that the computer running the workstations had rebooted. Shruggingly written off as a one-time event. A week later the same happened. And the week thereafter and the week thereafter ...
Every thursday morning we found the machine had restarted. Strange. Service was called in and they couldn't find anything wrong. It couldn't be a scheduled job : the thing didn't have a clock or a way to schedule things. Files were saved with a version number that incremented upon every save. No time/date stamp.
Next thursday the sysop stayed late to monitor the machine from his desk in the aquarium. This was the era where the computer rooms were all floor to ceiling glass walls so you could proudly display the hardware to visitors. We users called it the aquarium. The sysop always said the fish were on the outside.
Somewhere late the cleaning crew for the office got in and sure enough: one of the cleaners entered the "aquarium" and started dusting. The nova machine had a nice ledge with a bunch of toggle buttons. out comes the dusting brush .... and mystery solved. It turned out there was a problem with the machine. One of the toggles was a halt/reset and it was a bit "sensitive". They replaced that front panel , and then put a piece of perspex over it, and told the cleaners to only collect the printouts but not dust anything in there.
Note : if i remeber correctly this things was a Nova 3