None of us like electrical glitches! I doubt that the wiper switch is the culpret, there just isn't enough movement to stress the wires. The only way to check it is to take the &^%@$ clamshell cover off the steering wheel and check for continuity if the wiper switch.
You still may have a problem with the wiper motor itself. I would have thought that voltage would have gone through the motor from the pos to neg sides, but I am just a novice. But then, if the switch is off to the wiper, there should be no current there anyway.
See if you can find a wiper switch at a local junk yard and swap them.

Klaus
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(V♂LV♂s 1995 854T, 1998 V70R)