You obviously don't know how a beta works. Code changes ALL the time, build to build. Fixing or changing something in one area can cause an issue in a completely unrelated area. That's just how it is.
And because it's beta, builds don't have to be exactly clean of obvious bugs. It's not meant to be your primary OS. And going build to build you just have to go along for the ride. Most will be gone by the time it's officially released in September. (I say most, because it's impossible to have 100% bug free software. It's especially true for something as complex as an OS.)
It's a little ridiculous you expect perfection from a beta.