Hello, I had this issue quite often these last weeks and I found a simple fix in some situations : when I press play and the VR preview window opens, I put the HMD on, and I noticed recently that once the HMD is on, in some cases the unreal editor window is getting back on top of the VR preview. A simple ALT+TAB on the vr preview window got the hand grabbing functionnal again. Hope this helps someone.