This could be because they are beamed maybe? Please note that i used the menu, not a keyboard shortcut to do it, so that question is out of the way. Ive also been able to replicated over different projects, it doesn’t seem to be localized. See example:
Also, trying to do double/halve with a triplet in the middle generates unwanted results, as the note values are indeed halved, but not the base value of the triplet (from 8th notes to 16th notes, see example):
You need to active insert mode to allow Dorico to add/remove time. Be aware that this won’t move things like meters, key signatures, etc.
In 1.2, you can add tuplets to existing notes (!!!), so you might be able to clean it up by removing the tuplets, and re-enter the proper ones. You need to be in note input mode for this to work.
Tuplets are not scaled by the double/halve duration commands, by design – for now. I’m sure this will change in the future, along with the introduction of other commands to edit tuplets.