You should be able to select all, and filter for notes and chords. Take a look at the l.v. property – if it’s on, then toggle it off; if it’s off, then toggle it on and back off. This will remove all l.v. ties in the piece.
The ties appear to be correctly done in the Sibelius version, but then randomly some have been converted to l.v. ties when they are imported via MusicXML to Dorico. I am puzzled by this. All notes are in the same voice
Here is an example. This is the exact same bar in both Dorico and the original Sibelius version. As you can see, the low D on beat 3 appears as an l.v. tie in Dorico.
Was the tie encoded correctly (ie as a normal tie) in the Sibelius musicXML export?
If it was, then Dorico appears to be interpreting it incorrectly.
If it wasn’t, then the fault might not be with Dorico but with Sibelius.
When I delete the notes in Sibelius and re-input them with the correct ties, the problem goes away when I export to XML and re-import. But the ties that are being incorrectly exported do not show up as l.v. ties in Sibelius. There is no way to know where the problem will occur it would seem.
So my best option (I think) is to somehow be able to filter the l.v. ties in Dorico and correct them there.
What I am trying to make clear is that, even though within Sibelius they might appear as normal ties, when Sibelius exports the notation to musicXML those ties might be encoded incorrectly. The way to determine this is to post the musicXML file (exported from Sibelius) here so that someone who knows what to look for can check through that musicXML file and find how they are encoded.
When you exported the musicXML from Sibelius, did you use the built-in capability (File > Export > MusicXML)? There is a Dolet plug-in available which reputedly does a somewhat better job of exporting to musicXML. You could try that to see if it makes a difference.