Ensemble POV
'Head-hopping' in a murder mystery is not unusual. Limited 3rd-person POV can conveniently usher the reader through what they need to see, when and where it's convenient.
All events are filtered through the biases of a particular character, at any particular moment. Characters can be naive, suspicious, sidelined, and cagey – adding a particular spin on a scene regardless of what is happening in plain sight of the reader.
More interestingly, 2 characters can witness the same event and form different opinions.
The story continues to progress forward in time. When we are with Character A, Characters B and C are progressing offstage doing who knows what to the evidence. Time does not overlap unless you specifically indicate it by synchronizing multiple scenes to a common cue (a scream that everyone hears).
Some narrative untangling will be inevitable in a murder mystery where characters later recount where they were. Try to keep this clear as there are 2 timelines the reader needs to track – a puzzle 'mystery' which has already happened, and a crime 'thriller' which is currently unfolding. Both timelines inform/update each other as they progress. A thing learned in the current 'thriller' timeline cannot be un-learned when returning to the 'mystery', and vice versa.
It's not possible to fool all readers, but as author it is possible to fool several characters who must coordinate seemingly contradictory eye-witness accounts to puzzle out the truth.
Having your cake and eating it too
The problem with an omniscient narrator is it breaks all the nice rules of using the ensemble as first-hand POV. It undermines the main narrative device used to reveal the mystery and manipulate the reader through complicated biased eye-witnesses.
Adding an omniscient POV to the story is effectively adding a 3rd timeline, an entity out-of-time who knows the outcome to both the mystery and the thriller... but for some reason isn't telling us.
Now when Character A misinterprets what she saw, she is just 'wrong'. It's her character flaw leading her astray. The omniscient narrator always knows what really happened and should be foreshadowing her fate – commenting on the clues she's missed, and revealing her tragic mistakes. This is more in line with slasher-horror, coming-of-age, suspense –– all narratives that rely on tension, by the reader knowing something the character doesn't.
This reader tension is the opposite of 'mystery'. We are dreading what she is doing. We know she is wrong and heading into danger. It's not a red herring if the reader doesn't go along with the pursuit. This character is making a bad mistake and will probably die (or worse, waste the reader's time).
When we see this play out, it is to add tension to the 'thriller' timeline – the reader learns that Character A is walking into danger through an update/twist on the 'mystery' timeline, which the reader has learned through Character B's POV.
The stakes are easily raised through a twist reveal, without breaking the ensemble POV – there's no need for an omniscient narrator to signal what is happening through commentary or foreshadowing. The tension is baked into the unfolding plot.
Reasons to (not) do it anyway
An omniscient narrator undermines the ensembles' ability to uncover a sudden twist leading directly to dramatic tension. Instead there is always this 'narrator' who is safely outside the unfolding story.
The main reason new authors want to 'cheat' with an omniscient narrator is to show factual events they couldn't figure out an elegant way to reveal organically, because no one was in the room to eye-witness it.
This is terrible writing, don't do this.
It's expected that information from the mystery timeline will be unreliable, but to play fair with the reader most of the red herrings will be 'true' just misinterpreted by the witnesses. Even at the end of a red herring, the reader should be rewarded with some twist that changes the chessboard or reveals another clue. This keeps the mystery unfolding.
An omniscient 'camera' shows us what really happened. It's the one 'true' version of events from the only authority: directly from the author. Telling the events to the reader as a literal, un-mitigated fact robs the mystery of any mystery. There is no puzzle to solve. No meta-empathy is experienced by the reader synchronizing them with the characters through the pursuit of a common goal. We don't wonder whodunnit, This becomes a crime 'drama'. We're just waiting for the murderer to get caught.
Stylized exceptions, and possibly better options include:
allow the reader to use their imagination. The more engaged in co-telling the narrative, the more invested they become in the story.
a professional detective arrives to sort out this mess becoming a de facto omniscient narrator in charge of collating all the POV into one timeline. Have also seen a journalist recount the mystery after.
a court trial acts as a frame device, establishing 'facts' from the earlier timelines (murder mystery and crime thriller) as they are told through eye-witness testimony on the stand.
the deceased is a semi-omniscient narrator, able to comment in real-time on their own mystery, but unable to intervene or influence the case.
Greek Chorus is a way to insert the public's opinion because it says what the average person is thinking. Modern updates include 'the media' and newspaper headlines, or maid-and-butler dialog where people affected by the events share what they know. In a crime drama this is often forensic evidence delivered by a subordinate. These are presented as opinions or unfolding 'gossip' which can change as the truth is uncovered (not 'gospel' direct from the author).
Taking away the mystery by inserting un-questionable author 'facts' is the equivalent of telling the reader what happened, rather than showing the unfolding consequences on the characters, and allowing the reader to solve it for themselves.
