Replacing an old segment with new after re-confirmation

Hello! I'm been having a problem with Studio 2017 for a while now, but it seems to occur more often now. I finish translating a segment, then confirm it. If I change it after, the new segment does not replace the old one in the memory. Both appear. So I have to manually change or delete the segment that is incorrect every time. It is quite time consuming. It doesn't happen with every segment and I don't understand why it does that. Any ideas?