Is my baby un-sleep trainable?

On week 2 of CIO. Started with Ferber for 2 days and it made it worse. Baby is 5 months this week. There have been 3 days in the last 12 of less than 30+ minutes of scream crying. We do the same routine, same exact schedule every day. There are no inconsistencies.

She has always been very temperamental, fussy. I’m wondering if sleep training will never click for her.

I know the suggestion will be to add awake time but I don’t believe that’s the issue. She falls asleep very easily with assistance, almost immediately for naps (all contact). We have a bedtime routine of feed, bath, pjs, lights/sound, sleep sack, sing song. By the time she is heading to the sleep sack she starts screaming. However, there have been 3 days where she fell asleep in under 10 minutes with minimal fuss but the routine and time awake was exactly the same so I don’t understand it.

Schedule is 2/2.5/2.5/3 with naps capped at 3 hours.

I should also add that we really are struggling with this but I don’t know else to do as she is waking up hourly with a feed to sleep association.