Amanda, sometimes music XML is reasonably good but there seems to be problems in the way each software program either imports or exports it (how it interprets symbols etc.) I believe each is intending to improve this in their on-going updates.
I had a problem with StaffPad directly to Dorico using music XML but the tuplets were a mess as well as a number of other things so I tried StaffPad to Sibelius to Dorico and that worked much better.
You could try various imports and exports if you want to experiment. Musescore might be a good intermediate or Finale (although if the problem is the current Dolet it probably will not help as the data coming out might not be adequate). However because of my success with Sibelius (v8.5) to Dorico for a few other things, it might be better to try a more recent version for exporting as Stephen has suggested.
Another thought: each import-export might re-interpret the data in unexpected ways making it worse.