This sounds like one of two possibilities; resistance is halving damage, or some other modifier/die roll is influencing this. I think the only one that might be that I've seen is ray of enfeeblement (which actually shoulden't, but that's an easy programming oversight). If you're actually getting damage rolls of 1 then this basically has to be what's happening.
I will note that it's possible you are seeing resistance reducing it from 4 to 2, as Imps (a super common enemy at the start) are resistant to piercing. It might be worded as "resistant to non-magical weapons" or something instead, although I think BG3 breaks it down by type...If we knew what you were fighting we could say something more here.
Oh, and to answer the question-I haven't seen miscalculated damage yet, no.
