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Are you using effects like Bless, Bane, and/or Guidance?
Definitely no effects.

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Did your stats change?
Since Larian is showing pass number after they deduct(?) the proficiency ... instead of adding it to roll.
I am not sure about earlier encounters, but for the last one they didn't. I was lvl 4 then, I am lvl 4 now. However I did went back to kill an owlbear between the 2 attempts and the requirement jumped from 16 to 18.

My heart will take me there, where my feet cannot...