PS2 acts as if button is constantly pressed, even with no controller plugged in

I ordered a brand new controller from a third-party developer, plugged it in, and it worked fine. Strangest thing is that now the old controllers work too, but only as long as the new one is in the socket when I turn the machine on. As long as the new one is there on startup, I can switch them out and they work fine. But the problem persists as before if I don't do this.

In conclusion, I have no idea why this problem happened, but I did manage to "fix" it. If anyone else has a similar problem, I recommend buying a brand new controller, I guess.

When my ps2 controller started pressing buttons I was not pressing I took it apart & put a piece of electrical tape to hold the thin plastic piece (looks like clear scotch tape w/gold thin wires built inside of it) onto the circuit board. The under side of the ps2 controller (on the inside of the controller) has what looks like a piece of dark gray foam built into it that holds the thin plastic piece (looks like clear scotch tape w/gold wires built inside of it) onto the circuit board. The electrical tape I put there assists the dark gray foam piece in having to do it's 'job'. After doing this my ps2 controller worked like new again.