Really odd question, but do you have, or have you recently had, painted toenails?
I hardly ever do this - too much faffing around, and nobody to see them anyway. But a few weeks ago, I did it on a whim.
Not long afterwards, I took my shoes and socks off, to discover the tip of my big toenail had literally snapped off! I don’t remember that ever happening by itself before, as the result of normal wear and tear, so I can only conclude it had to be something to do with the polish. But it wasn’t extra tough, strengthening polish or anything - just the normal stuff. So I wouldn’t have expected it to reduce the flexibility of my toenails to the point they might snap. I’ve never had that with fingernails, although repeated applications of polish and remover do tend to dry them out and make them brittle - it’s mostly the remover that does the damage, not the polish. But remover had not been anywhere near my toes - it was the first time I’d painted them in years, so I couldn’t blame it on mistreating them. If I’d thought it would make the nails break, I never would have done the stupid polish!
I know nail polish by itself couldn’t explain the difficulty getting your boots off (I always have that anyway, to the point the neuro, if he needs to examine my feet, asks: “Are you able to get those off?” “Er…yeah. If you’ve got ten minutes?”) But I just wonder if it might explain the nail fault problem? Mine were fine pre-polish. Won’t be doing it again very soon.