What exactly are we looking at? Can you step back an bit for a wider angle pic. What is that material? Is it oozing out? You need to help us help you.

Based off of my other research this is a sign that the tile shower is failing due to improper installation. I don’t want to redo the shower and looking for a simple solution.

very possible you might need to go over and inspect further

Definitely you need to go over and inspect better. No way of knowing anything from that little snippet of info.

And if it's improper installation and waterproofing there is no simple solution. The only solutions is a full tear out and redo.

Bandaids never work on a gushing artery. 😐 If the shower was built incorrectly, there is no kludge fix. There’s only demo and replace by a knowledgeable contractor.

Additional pictures and details are required to even begin to figure out the issues here. But mushy wet drywall is not good.

See I was expecting everyone to say it needs a full demo and to be redone. Based off my research it’s definitely from a failed install. Could it be possible to grout caulk all the joints or would that just be absolutely absurd? I understand the way the tile shower works with the water actually leaching behind and draining in a secondary drain in the pan. But is that even something to consider?

you really cant give a diagnosis until it is inspected in person

"See I was expecting everyone to say it needs a full demo and to be redone."

Quite possible that will be the answer but until we have more info no one can accurately say, including yourself as all you have seen is one picture that really shows nothing.

I scheduled to do the service work on this next week and I’m just trying to get more information on the possibilities that something like this would occur. I’m aware humidity could cause damage. With the photo and these details, “this spot had shown water damage at one point and drywall repair was done. Weeks later in the same spot drywall begins to bubble out.”

If I were to start by removing drywall back to the concrete board what should I expect to see? What signs diagnose which problems?

I have to say that is kind of odd. Look how far that is from the main shower and how far up the wall, but very little damage below it to the drywall. If that is a waterproofing failure and water has managed to so saturate the substrate like cement board, and wick that far over to the drywall, I'd expect to see more drywall damage below it as the water just poured in there.

Could be all kinds of issues. The drywall corner detail could be bad, meaning that the whole shower is waterproofed correctly other than the drywall is lapped the wrong direction in front of the waterproofing behind that corner piece.

Could have massive waterpoofing failure and a completely saturated substrate from water migration.

Could have a plumbing leak that is running through the framing.

Could have a bad pan that is wicking water up the wall. This is especially likely if it is a traditional mud bed and they did not do a pre-slope. No pre-slope essentially means you have a lake sitting on your shower floor at all times, so if there is a waterproofing failure you are more likely to pay dearly for it.

You could also have a humidity/temperature problem. I've seen it where if the bathroom is not well insulated in winter or if someone runs their air conditioning really cold like 65 or below and is a bit cold, then someone goes in there and takes long hot showers those metal corners get really wet like a pop can in summer and the condensation is so extreme it damages the drywall. In this case a bead of caulk really could solve it.(if you are that lucky go buy a lottery ticket because you are on a roll.)

Opened it up and it’s dry behind corner bead but slightly moist between corner bead and tile. Plumbing is 24” away from wall damage and no moisture from the bottom or top