A broken rudder return spring won't contribute much, if any, to
the stop-locking problem, but it will make the airplane fly cockeyed
unless you hold pedal pressure against the good spring. We used to run
two 150s, and had (and still do have) springs break at various times
both in the 150s and 172s. The pilot complains of really bad rudder
trim. The rudder cable tension is determined by the springs, and isn't
very high at any time.
As I said earlier, the stop bolts don't wear that much. It's worn
hinges and loose bellcranks that allow the little hook on the stop to
ride past the bolt head and get caught. Ironically, it's the same
little hook that's supposed to prevent the override. Seeing a good stop
doesn't mean there's no problem. There are likely very few 150/152s
like this, but it's worth getting it checked at annual. The new stops
have no hook and are much longer and wider, and the stop bolt has a
larger head.

Dan