Strange Molting Habits?

[folkjam]

Hello everyone,
I have had two medium-sized crabs for about a year and a half, and only recently has one of them shown any desire to molt. He has very slowly been digging, but it has taken about a week, and not always in the exactly same spot, meaning the entry hole is fairly large for his size. I have about six inches of substrate in the tank, and he is now down about two or three inches inches and seems to be settled. However, he is still very much visible and uncovered by the substrate. I don't see any signs of a shed exoskeleton, just the crab withdrawn into the shell. I even found his tankmate laying on top of him this morning, which I then moved to the other side of the tank.

Is burrowing but remaining uncovered normal for molting? I've been reading the forums, trying to find another experience like this, but have been unable to do so. I'm hesitant to add any more substrate, as I don't want to fill up the pockets of air that he's made for himself. Any tips would be greatly appreciated, as I've never dealt with this kind of behavior and want to make him as comfortable as possible. Thank you!

[curlysister]

What are you using for substrate? Has the other crab molted at all?

[folkjam]

I'm using Fluker's substrate. The other crab hasn't molted either, strangely. He dug a tiny divot in the sand yesterday, but hasn't bothered since. I'm keeping the appropriate humidity, swapping out fresh water and food daily and everything else I've read.

[curlysister]

Is this what you are using? Is it moistened with dechlorinated water so that it is 'sand castle' consistency?
https://flukerfarms.com/hermit-crab-sand-substrate/

Can you post a photo of your set up?