When writing with multiple voices per staff, some collisions may appear like this :
Of course I can correct this in engraving mode but is this a bug ?

That’s a lot of voices. Do you intend 3 voices in the top staff?

You do not show enough of the measure for anyone to give an informed opinion.

Yes, here is the difference :

Just tried this in 2.1.10 and couldn’t reproduce it, neither natively in Dorico nor by MusicXML import. However if the XML import options in Dorico are active for rest duration and vertical placement, data in the XML file may cause the erroneous placement. However, I could correct that by doing edit/Reset Position… fwiw