I'm by no means a nem expert but maybe it's not fully opening because it's eating so much. It doesn't need photosynthesis for energy at this point so it may be staying closed because there is no reason to open up.

Thanks for the info on the nems. I will cut back on feeding him and see if things change.

Keep us posted on how things are going

I would also say to not worry too much about it, unless things are dying. I have two different kinds of frogspawn that inflate and collapse at least a couple of times a day, operating on a schedule that I have yet to figure out. Most of my LPS are like that actually. Up and down, up and down. I have one brain coral that's actually figured out the schedule of the auto-feeder, and opens up to it's fully engorged, tentacle out feeding state (normally something you only see at night) promptly at 2:45pm every day. The feeder drops pellets almost right on top of it at 3.

Also, when you feed LPS or nems a lot, they also poop a lot. When they poop, they completely deflate and look like they're about 3 seconds from death. If you happened to be walking past them at that very moment you might think they were sick.