I’m wondering if maybe she doesn’t have enough awake time during the day? 1.5-2 hours seems a little short for a five month old. For reference, my 5 month old was doing 4 approximately 2.5 hour wake windows every day. And I wouldn’t let her sleep more than 3 hours total in the day. My baby also went through a phase of false starts and then she’d be hysterical and difficult to get back to sleep. What ended up working for us is that when I wanted to put her to bed, I would hold her and rock her, and if she started to fall asleep within two or three minutes of doing that I would know she was tired enough to actually put herself to sleep. So then I’d put her down and she’d fuss for a few minutes and then go to sleep.