Condensing - horns unintended key signature change

I have imported 6 orchestral projects from Dorico 2 into Dorico 3 yesterday and I see that my HORNS in F when condensed change back in concert pitch (though transposed pitch is selected) at a certain point about 21 bars into the piece.

I’m not sure why this happens, or how to make it not happen.

Can you please attach a stripped-down version of your score? Zip it first; the forum site doesn’t accept .dorico files.

Please see this earlier thread and this one.