But first, you had 3 races going on? Did they all start at the same time? or did they have time offsets? (6am, 6:30am, 7am....) Or were there wave starts for the same race?
I ask because, if you put the bib in the wrong start race or wave and manually enter the time, they would account for the wrong time showing. The software is calculating the start offset versus the running time and either adding or deleting time. That is one possibility.
Also, if you had stepdown races running and put them into one of those clocks, that could also explain.
But I think the more likely issue is this, and you can check to confirm:
I think you had the same entry in 2 or more of the events (bib and information). Even if you had all clocks running, the software is fighting itself over where to assign the chip read between the 2 or more events. Likely it put the read in the wrong event. In this case ART sees it has already finished, so ignores it, so it doesn't also put it in the right race.
I had this happen not long ago. It was my fault. I do not sync to registration sites, so I manually import from a spreadsheet every time. Therefore I made the mistake. To fix this I deleted the participant from the event they were not supposed to be in and ART automatically assigned the time to the same bib number in the right race.
Not saying this is what happened, but this might be what happened. Best of luck!