For skillchecks there might be mali at play here that are not displayed. Like I had a +4 Persuasion role, yet rolled a 4. There were only a couple skillchecks that I failed multiple times and I would wager that it is because some modifiers are hidden from you, which I do not think should be the case.
I have not seen something similar in combat though and I do keep rough track of things like this and for me they add up so far. Especially since they give you a breakdown of how these percentages come to play in the bottom left corner. But there might be some hidden stuff there as well, or things you simply miss. Like debuffs, buffs etc. and this might affect the dice after the roll as well. So the log shows a 19, but there is a +1 bonus from whatever, hence a crit happens. This might not show up in log or does so separately, or hidden or somehow obscure.
