1.
There's a chance the contacts inside need cleaning. There are spray solvents called 'instant contact cleaner', etc.
Squirt some in all the openings, while you operate the switch. It may remove dirt, grease, lint, etc.
2.
Do you suspect parts are broken inside? This is likely to render it useless. If you are inclined, open it up and you may find you can fix it. Then wire it back together.
3.
6 terminals means it is probably DPDT. With a push switch that will take a lot of weight. It's a type that you would not find just anywhere. (Most DPDT switches are toggle or slide type. They would soon break in use underfoot.)
Have you checked for a replacement at a local music store? Ebay?
There are websites that show how to build guitar effect pedals. Some are bound to use a DPDT foot-switch like yours. Check out such articles. One might list a supplier for the switch.