@mtag Deco X50-Outdoor is likely what will resolve your situation. There are a number of configurations utilizing it which could work. It is compatible with M5. If it were me, I would purchase one, place it just outside of the house on the side facing the barn (maybe on the roof, or mounted on the side as high up as you can go) and see how that does getting the signal to inside the barn. If it is still not strong enough, then I would purchase a second X50-Outdoor unit and put it just outside the barn (also on the roof, or mounted on the side facing the house). The second X50-Outdoor unit would certainly provide the strongest signal, however would be more expensive. I would keep all of the M5 units inside the house as you originally had them.

https://www.amazon.com/gp/product/B0BKPRCS6W

  @H242  one x50 outdoor unit set up just outside the house, with an m5 inside the barn, works perfect. We can steam video from inside the barn in the farthest corner. Thank you! 

  @mtag That's really awesome. Congrats! I'm very happy that it worked for you without an enormous amount of effort or playing around to get it to work.

Best regards.