So, this is an interesting one.
I opened up an old score in Dorico 3 and saved as a new filename (with Dorico 3 on the end) so that I could test things in the new version without altering the original file.
I was changing artificial harmonics in an old score from the old method of notation to the new method. After doing this, I lost the slur between two artificial harmonics.
To verify that the slur was actually there originally, I opened up the original file in Dorico 3 (without Dorico 3 on the end of the name) alongside so I could compare as I was working so that I can add the slurs back if they get deleted accidentally.
Now whenever I delete the old-style touch 4th from the new Dorico 3 file (by selecting the touch 4th diamond note and pressing the delete key), it deletes it, but then my window focus somehow automatically changes back to the original file and I have to click on the Dorico 3 window again. This is happening consistently.
Any ideas? I think this is a bug.