Also watching a stream on twitch a guy needed 0 and got -1 ....
This sometimes happens when you roll a 1 on Illithid checks.
Right now a 1 is an autofailure on skill/ability checks, and my guess is it conflicts with Illithid checks since their DC is 0. 1 should beat 0, but because 1 always fails the check the game has to change the roll to -1 to make sense of things.
Not sure about the other ones. Maybe the game didn't count the modifiers properly?