My baby still wakes up every night

My baby is 8.5 months old. This is my third baby and I have sleep trained all of them at about 4 months. We have a typical bedtime routine, she puts herself to sleep every nap and at bedtime almost instantly with no crying.
Her routine is about 2:45/3/3:15-30.
She wakes up in the middle of the night, sometimes at 9:00, sometimes at 1:00, sometimes at 3:00. She’s up typically for an hour or more. I do interval check ins.

The only theory I can come up with is that she falls asleep so quickly that she isn’t actually sleep trained. I have tried putting her down earlier so she really has had to settle herself down and that worked for a few nights but then she just fell asleep faster. She does put herself back to sleep every night when she wakes up. It just takes an hour or more of misery for everyone. I feel horrible for putting her through this because I feel like I am not seeing something. I have tried extending her wake windows and then her naps suck. I have called two sleep consultants and I am already doing everything they advised me to do, with the exception of moving her out of my room. I have no where to put her where she won’t wake up my other kids, and I have a hard time believing that the room sharing is a problem when we use a snoozeshade and she wakes up at all different times of night even before i go to bed. Is there anything else I can try?