A major revision was submitted to a journal. After some days, the status changed to 'awaiting reviewer scores', but there is also the status 'awaiting decision' right next to it. How should this double status be interpreted? Is the revised manuscript with the editor or reviewers, or both?
Here is a possible interpretation: the paper might have received the comments of all of its reviewers. So, its status is "Awaiting Decision". But the editor, for some reason, e.g., conflicting opinions in those comments, has sent the paper to another reviewer. Thus, the status also reflects "Awaiting Reviewer Scores".
Nobody here can tell you what is happening with your paper. However, I will give a possible interpretation that is slightly different to @Robotocist:
Often people decline invitations to review papers. If an editor wants, say, two reviews for a paper, they may initially invite four or five referees. Once two have accepted they will typically cancel the other invitations. However, if they are too late to do so, they can end up with more reviewers than they really need. The system will continue to show "Awaiting reviewer scores" until all reviewers have submitted their reports.
Meanwhile, the editorial management system will be configured to automatically mark the paper as 'ready for decision' once the minimum number of reviews has been submitted. However, it will still recognise that not all the reviewers who accepted have submitted a report. It is up to the editor to decide what to do - they may choose to make a decision based on the information they have, or wait for the additional report(s).
Unfortunately, there is nothing you can do except wait, and you should not take this as providing any information (positive or negative) about the eventual outcome of the review process.