I'm not a tuner by any means but from my research it seems like the issue happens when its cold and going from open to closed loop. I think during that period the ECU is "hunting" for the right AF and it takes a second to find it due to TGV's not being there.
I recently read something on PhatBotti's website that it was normal and could be helped but not always completely corrected. I'll try to find it again.