Well, I will state the obvious; it needs to be serviced before there is some irreparable damage done to the mechanism.
Of course, it probably would be cheaper to simply buy another used, but fully functional camera body rather than pay for servicing the camera.
Ebay prices for functional bodies start around $60 USD and go up. A repair might cost less, but most general service for any problem will exceed the cost of replacement, in my opinion.
You could always try to fix it yourself. Here is the factory repair manual:
https://learncamerarepair.com/product.php?product=222&category=5&secondary=49
Here someone has an identical problem and another person makes a suggestion to fix it, but there is no followup as to whether it worked or not, but it sounds like a reasonable repair attempt:
https://www.photo.net/discuss/threads/x-700-switch-problem.5494240/
If you have a nearby camera repair shop, you could always get a quote.
Good luck.