Interesting issues when importing Sibelius 12/8 file across via music xml into Dorico 5. Any triplets (3:2) over two beats caused issues with extra 8th note added to the bar, shifting of other rhythms and consequent flow ons in other parts, and the triplets not being shown correctly. The only way around was to delete the triplets in Sibelius, export via music xml and rewrite the triplets in Dorico. It worked but was quite a journey. 12/8 issues only and/or music xml?
Finale gives XML trouble with triplets as well. It appears each program interprets triplets a different way (dividing by 3 in a computer’s base two system does not work well), which gives Dorico (and perhaps other programs) trouble importing them.
Interestingly, other files I’ve imported in 4/4 time and full of triplets have had no issues. Just the 12/8 spooked it!