Sounds to me like somebody sent you one that they bent the pins over and then bent them back before selling it. That is the ONLY reason that the pins would have broken off.
The Gravis gamepad and Gamepad Pro are good controllers.
They do have to be taken apart to have the button contacts cleaned out after years of use though. By that time, the rubber in the buttons is most likely starting to fail as well.
Same goes for any controller be it for a console system or PC or whatever.
I've been using Gravis gamepad and Gamepad Pro controllers since they were released. They really are nice controllers when they are working properly / taken care of.
We finally replaced the one my father had after many years of use because the plastic on the buttons had worn down it was used so much. Pretty sure I replaced the rubber direction pad and rubber buttons either 2 or 3 times before I got him a new one.
Whenever I get a faulty controller I will save the rubber button parts. I have a pretty big collection now. Most of the ones I have came out of broken console controllers.
Some other things to think about are:
What sound card or gameport card are you using?
What are the specs of the rest of your computer?
Back in the day, the older gameport cards and pretty sure some sound cards would not handle faster computers properly and controllers would either not work at all or they would be flakey.
Then they came out with speed adjustable gameport controllers.
A lot of the old dedicated gameport cards and sound card game ports do not support more than 2 buttons or would drop from 4 buttons to 2 buttons per controller if you had 2 controllers hooked up.
The Gravis gameport controllers with the adjustable pot setup (have a cord with a speed adjuster that plugs into the card) support 4 buttons.