I have down loaded Affinity Beta and evrything was OK from the Raw through to adjustments. After working several layers, they would not flatten. The flatten bar just continually scrolled for 15 minutes, then disappeared. The stacked layers were still there, they had not flattened. Before writing this part of this post, I have just ckecked and the stack has flattened so there is some delay between clicking to flatten and actually flattening the layers. So it seems to work, but there is some considerable delay.