Might be similar to the issue that I've had for a while now. It seems that if I open a project and attempt to preview it will be black. If use worker is on it will remain black, if not it will hang for a bit then load. The workaround is to switch use worker off then run the preview once. After that you can turn it back on if you like and it works normally
That's a different problem I have it too, it's been for a while now, I think like 5 Moths or more, it looks like its permanent as they haven't fix it yet