Night 6 of CIO (re-training) and still screaming like a banshee

30+ minutes of screaming at the top of his lungs on night 6 of sleep re-training. We’ve been doing CIO with occasional check ins to get him to lie down (he’s standing and screaming). He’s 8 months old, we try to do 3/3/3.5-4. Please help! I’m losing my mind hearing him almost lose his voice from screaming. When we originally sleep trained at 6 months it only took 2 nights and 15 mins of crying.