Hi!
I had "shell-less eggs problems" with several hens in the past...
These hens laid more and more shell-less eggs, and... I think the cause was genetic : they had no worms, nor lices, nor mites, nor diseases or whatever... and since all of them were hybrid chickens, and I am pretty sure they were coming from the same place, a genetic disorder just seems likely to me...
...An unlimited access to oystershell grit did not help.
Giving them liquid Calcium specifically made for poultry did not help...
Feeding them yogurts, eggs, cheeses, herbs, etc... did not help!
Nothing I tried helped then...
...At least, until I just decided to do an experiment with food grade Diatomaceous Earth.
Indeed : several months ago, I had decided to mix food grade DE with my chickens' food... (Primarily given the fact that DE is told to have Calcium and plenty of good things!)
And then : I was so satisfied with the results that all of my birds have now an unlimited access to food mixed with DE... everyday! And CLEARLY as a result : for all of these (several) months now, my hens have NEVER laid any shell-less egg anymore.
(Actually, all of my hens are now laying eggs with thicker eggshells, and some hens even lay, VERY often, double-yolked massive eggs...!)
(Knowing I only mix food grade DE with the pellets, wheat, and Premium Mix I put in PLASTIC feeders...
The metal feeders have not DE mixed in the food...!
Thus : my hens do NOT eat only, or have access only to food mixed with food grade Diatomaceous Earth.)
...Voilà.
You do what you want to with this information!
Good luck with your hen.
Could be nothing to worry about...
Problem might even be temporary here and go away on its own...!