Is anyone else experiencing recurring issues with grout on their propane fireplace stones detaching from cement board?

I have a propane fireplace in my house, which is only 5 years old. I’ve already had to change out the stone on the fireplace once before, and now I need to do it again. The first time, I thought it might have been a grout problem, but it’s happening again. The stone and grout are stuck to cement board. Has anyone else had issues with the grout coming loose like this?