I went to treat mine today, but they were all running around the top of about four of the broad frames, not clustered down in between "as it says in the books" will have a look in a couple of weeks.
Yes mine too but no issues in treating them. Used this method /s today.
Puff of smoke, remove brick or release strap, remove roof, insulation and empty super, second puff of smoke, lift crown board at rear to almost vertical, wife passes freshly loaded syringe of room temperature oxalic solution, apply 5 ml per seam of bees, lower crown board and rebuild hive. If loads of bees milling about on frame tops another puff of smoke will send most of them down between the frames long enough to apply the oxalic.
If adding fondant prepare it for application by slitting film before removing crown board, after applying acid puff of smoke to clear top of frames, add fondant, add empty super, tap bees off crown board in, another puff of smoke, add insulation, crown board and roof. My insulation is cut from space blanket and shoved in pillow case so it moulds over fondant without squashing bees.
Alternatively add fondant over feed hole in crown board, ensuring its above cluster area by turning crown board as appropriate, then super, your chosen type of insulation and roof.
30 - 90 seconds with the crown board lifted per hive depending on if adding fondant or not.
Not in the books as such but it's my variation on a theme and works for me, other opinions will be along shortly.
If the mild weather continues brooding will start in earnest soon and the mites will be tucked up safely sucking the life out of the larvae.
Bit more smoke than I usually use but it moves them.
