[dshcs]

I am starting to get some “grout” failures in my shower. I don’t know how it was constructed (remodel) before we bought the house 8 years ago. The shower walls seem to be acrylic (the floor is real tile), it sounds thin and hollow when tapped (not real tile). Looking at what products are on the web today, they all seem to be acrylic sheets and not individual tiles. As you can see in the pictures, my 8” x 10” tiles seem to be individual and not a sheet. The “grout” lines are not perfect like you would expect in a sheet and if you rub your finger nail down the "grout" lines, they seem softer than the face of the tiles. I could not find any acrylic tile products on the web, so I am confused as to what this stuff is. I would like to know what product I am working with and how to approach the “grout” issue. Does anyone know what this stuff is?

Picture #1: single tile
Picture #2: field joint

 

[Blondesense]

Sometimes it is hard to tell from just a pic.

What do you mean by "grout failure?" Or do you mean the caulking? If it is a caulking issue, removing it and inspecting the exposed edge will give you a better idea of what you are dealing with.
A close-up pic of your problem area may be more helpful.