Night wakes getting worse

Hi! I have an almost 7m who was sleep trained at 4 months. He puts himself to sleep without fuss for naps and bedtime.

He was down to one night wake for awhile and a few weeks ago started back to waking every 3 hours all night. When he wakes he will scream and get increasingly hysterical. I will leave him for awhile and he won’t go back to sleep. The only thing that helps is nursing him, but I do not think he is actually hungry. Longest I’ve let him CIO was 50 mins. When sleep training him initially he never took more than 30.

I wondered if the issue was that he was ready to drop to 2 naps so made that change almost a week ago. That fixed the issue we were having with inconsistent naps, but night wakes remain unchanged. Schedule is 3.5/3.5/3.5, naps capped at 2-2.5 hours. Bedtime is 7. DWT is 6:30.

Any ideas welcomed!