Eggs sometimes dent before they pip.
Sometimes they dent from too little humidity.
I had two eggs dent early on this year that popped back out when I added damp moss.
I suspect in your case they are denting in preparation for pipping. You can try adding some damp (but not wet) moss. Last year same thing happened to some of my eggs a few weeks before hatching, adding humidity did nothing to reverse the denting - and they hatched just fine.
The eggs that didn't dent hatched last. The one that dented the most hatched first and is my best feeder from the clutch - very healthy, no issues whatsoever.
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3.6 L. getula californiae - 16 eggs (Cal. King)
1.1 L. getula nigrita (MBK)
1.0 Pantherophis guttatus guttatus (Corn)
0.1 Pituophis catenifer catenifer (Pacific gopher)
3.3 Elgaria multicarinata multicarinata - 14 eggs (Cal. Alligator Lizard)