Were you doing speed deadlifts every week when you ran conjugate? If not, that would definitely explain it and either way it sounds like it might just be a lack of practice since you are doing only one work set a week now. What do you do on volume day, power cleans? You would probably do better with deadlifts for volume day, there is no reason you can’t recover from pulling twice a week if you don’t do too much of any one day. Just start with conservative weights if you are going to add another DL session.