The viewport is shifted by the IVideoRecordingSystem::SetRecording call.
This problem occurs in play standalone mode and packaged build running as window mode. (not occur in fullscreen mode)
The viewport is aligned correctly when the window is moved or resized.
The viewport is shifted to left top corner.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-151821 in the post.