Hey got the same problem here in 4.16.3 !
But when I hide the cursor by setting bShowMouseCursor at false in player controller it’s completly fixed (again the bug is happening only in standalone) ! Seems to me that it’s related maybe to the high precision by the look of this code :
if ( bCursorHiddenDueToCapture || !bShouldShowMouseCursor )
{
ReplyState.UseHighPrecisionMouseMovement(ViewportWidgetRef);
}