Unreal Engine 4.22 Preview

Preview 3 is giving me some kind of ‘lag or temp.’ editor freezes whilst having RTGI/Reflections/Translucency enabled (lowest possible settings).
Didn’t have this in Preview 2. In 2 I could have RTGI on all day on default settings and only crank settings up for a final screenshot.
Now I need to turn RTGI/Ref/Trans completely off in order to be able to work.
The lag (or whatever it is) starts occurring after first time usage of Play level (current window/new window etc doesn’t matter) and gets exponentially worse upon repeated usage of Play Level. After a while I need to reboot the editor cause it’s become almost completely unresponsive.

Tested the same scenes in 4.21 and 4.22 (preview3 but without -dx12 shortcut) and that works fine so it’s highly likely related to the new raytracing functionality and then something that has been added ONLY since preview 3?