This is a hive configuration issue easily controlled in the horizontal hives - again, use those dummy frames and condense the bees to only the frames they can manage.Since wasps and yellow jackets are active at lower temps than honey bees they are able to attack a colony while the bees are clustered on a too cold to fly fall day. Easy access as there is no resistance....
I don’t know what your weather is like there in Utah, but in the Spring the yellow jacket queen is looking for a home, so kill whatever you see at that time of year. A big difference in amounts of YJ bothering hives later on.I had car issues last fall and couldn’t make it out to one of my apairies for a week, when I finally went to check on them they were getting over taken by yellow jackets. I closed off the hives for two days and placed traps around the apiary.. when I opened them on the third day all chaos ensued.the yellow jackets were flying in from all directions. I easily killed two to three dozen with my hive tool in less then ten minutes. Long story short I lost two hives to them jerks. This year I’m gonna try using fipronil and a stinky can of cat food.. hopefully this will work out better than the 1 liter soda bottle trap.