****Chiming in on this thread, 16 months later, because I have encountered the same problem, and solved it. At least for Sibelius 7, exporting directly (not using the Dolet plugin).
I am using Sibelius 7.1.3, and exported a hymn with 6 verses as uncompressed MusicXML. When I imported the MusicXML into Dorico 3.5, I found that my 6th verse was overlaid on top of verse 1.
In reviewing the MusicXML, I noticed that the encoding for the first staff looked like this:
Notice that last line, and the “number” attribute. It is “part1verse0” when it should be “part1verse6”.
I used my text editor (Notepad will do) to search-and-replace
I saved the MusicXML file, and it imported into Dorico correctly.
(No, I don’t think Sibelius users should be double-checking MusicXML exports; yes, my day job is being a software systems architect.)