Hi. I'm afraid that I've never had this problem with my colonoscopy prep in not being cleaned out enough. However, I am a small female and underweight at that. Do know that whenever I've done the prep I've pretty much spent the whole evening on and off the toilet. Never have had the magnesium citrate included as yet. Only time it's been included so far for me, I believe is when I had either the pill cam or the tube down the throat. Can't remember which though.
Were you successful the second time? Hope all went well for you. Good luck