How do I prevent the bathroom door lock from being "accidentally"
locked from the inside?

It is a Weslock with a cylindrical button on the inside next to the
doorknob. A previous owner drilled a quarter inch hole on the outside
opposite the button and I can see the butt end of the button through
the hole. From the inside I can turn the button a half turn and it can
easily be wiggled a lot, so is quite loose. I cannot get it to lock
when I try, but sometimes when exiting and closing the door behind me
I later find I cannot turn the doorknob and am effectively locked out.
I think the think is broken because I cannot get it to lock, but that
is OK as long as I can permanently keep it from "mysteriously"
locking. Obviously, I can just put a new one in, but if there is an
easy way to disable the locking mechanism that would be preferred.

Bill