I am in the middle of a house build in Keller, and my builder is not addressing our concerns about the shower permabase and pan liner.
Does the all knowing Home Improvement board know of a shower expert in the NE Tarrant County or DFW area that can help me with a plan to get the showers addressed?

I am not in your area, but am about to start a $10K master bathroom reno at my personal house due to a faulty shower installation.

I have researched shower manufacturers products & red specs until I am blue in the face and might be able to provide some additional insight. I built some houses in DFW a few years ago so I can see things from the builders viewpoint as well. Happy to help if need be.

What's the issue?

... if they don't then best Dutch Uncle advice is to
FIRE the SOB ASAP

If you don't know WHO the sucker IS at the poker table .... (it's you)

Ignoring you = taking money as if entitled to it, akin to rape IMHO

The ideal builder experience is that everyone is looking over each others shoulders to INSURE NO mistakes, no unhappiness later on = architect, builder, owner (not relatives!) ... inspectors, such as they are