This is quite the annoying bug. I have recorded footage on this thread here where I discussed my version of what is happening.
It seems to only affect my BP, any BP I create, and I choose to build my level, everything vanishes, but when T toggle any setting in details they reappear. The worst of it, is that when I try to make any change to the BP position in the Viewport, the BP actor disappears, and I have to toggle to view it again.
I have a video recorded at the very bottom (Do not open the others, your eyes will thank you later.)
If you can find something else you could figure out through my horrible quality video, or just in general, I’d love to know!