She's almost 2 now. Along with a possible physical growth spurts that could be throwing off her body rhythm, she's certainly making some cognitive gains, which may mean she's feeling insecurity, anxiety, or worry that was just never a part of her consciousness before.
If she is settling down easily when you simply come in the room, I'd say it's something on her mind. Reassure her that she is safe, that you are there, that you will be in the next room and you will see her in the morning.
That being said: Ear or tooth pressure often only hurts (or hurts much more) when we lay down. When she's been in her crib for a few minutes, her ears may start to hurt. When you come in for extra snuggles, you raise her head and the pressure relieves... plus, it's just nice to have mom or dad there when you don't feel good. Pressure pain wouldn't really get better with several trips, but she may just be getting so tired that she falls asleep despite the pain.
I don't know how much language she has. Have you asked her what's wrong? Obviously she won't describe in detail, but she might be able to set you on the right path (pain vs fear).
HTH
T.