Baby during bottle feeding

I need your help. My daughter is 4 months old and she’s been formula fed since she was 3 days old. I use the dr browns bottles since the beginning.

We never had any problems, but recently she started crying. Sometimes before I give her the bottle, sometimes during. And the weird thing is that some feeds go without problems and some are terrible. With her even refusing to drink more but if I try a little bit longer she will take the bottle again.

When she started doing this I went from the number 1 nipple to number 2. She does drink faster and better but the crying hasn’t changed.

Anyone know what this can be? The bottle isn’t too warm, she isn’t teething or has a ear infection.

I’m considering getting a different bottle. Would that work? And which one would you recommend then?