Pentair 08434 deteriorating

[Cooldood]

I have a 30 year old in ground pool.
One of the return jets pops out every now and then. It seems the threads on the wall mount have started to erode, so the lock ring cannot fully tighten/bed down and the jet escapes sometimes, likely at start up, or solar coming on.
Do we think the part in the wall will unscrew, or will it have been cemented to the pvc pipe during construction?

Here's a pic of the unit with the jet and lock ring removed.

 

[Texas Splash]

Cool, have you resolved your issue yet? If not, let us know. We will tag an expert who should be able to answer.