I have a Riobel DB150BN lavatory drain with a push pop stopper. The stopper all of a sudden when pushed will not pop back up. In the past when this happen a few extra push it would eventually pop back up but this time after numerous tries it seem to be stuck in the close position.

I unthreaded the stopper but it is not clear to me where the problem lies. Is it a stuck/broken part inside the stem? Does WD40 or liquid lubricant help or do I need to replace this piece?

There is probably not one single cause or component that makes it not pop back up. The Pfister push drains(we have discussed Pfister push drains before) are so inexpensive and work so well that you should just replace the Riobel with Pfister and be done with it once and for all.

By replacing the Riobel system with Pfister Push, you can solve the drainage problem, as Pfister is a more reliable and inexpensive alternative that works effectively and lasts a long time.

The problem is I have 4 of these installed.

I just called Riobel and they will be sending me a replacement "clicker" is what they call it. I asked if the clicker can be fixed such as soaking in vinegar or whatever and they said no just throw it away. They sounded like this is pretty normal.