Water coming out of overflow plate when showering

I have a fiberglass shower/tub combo.

I just noticed last night that while showering, there is water draining out of the overflow plate. It is coming out at a pretty steady pace.

I'm not sure why this is the case since the water from the tub drains fine. On the first floor, below where the tub is, there is a small damp spot on the ceiling.

What would cause my overflow tube to fill up with water and drain water from the plate? I imagined if there was a clog somewhere in the drain, that there would be water pooling in the tub, but the water drains fine.

And how could this be related to water leaking causing a wet spot on the ceiling below.

I don't have a picture of my tub, but here is one that looks similar: https://tinyurl.com/kmuw4f4

What type of overflow? Slip joint? Schedule 40? Pictures behind the wall would help

That weird! I thought I posted a reply to this post.

Water is not coming up from over flow drain. Something leaking back inside the wall and running down to the over. There is a gasket between overflow and the tub that has probably failed.

It is most likely the tub spout leaking back into the wall when you divert water to the shower hear.

Exactly David .very good

I wonder if you have one of these

a waste and overflow with a condensate drain opening

depending on the type of waste linkage, perhaps when the tub is full of water with stopper engaged
the over flow fills up with condensate?