iPhone keeps shutting off after battery replacement

Hello everyone. I followed the battery replacement guide almost perfectly with slight deviation. Turned my phone on and noticed that after about 10mins the phone would shut off (go into the white apple logo). It would maybe turn off and on a few times before booting back into the logging screen.

I did a hard reset and opened the phone up and made sure the battery was not loose. I disconnected the battery how it says in step 10-12 and reconnected. I turned on the phone and it works fine for longer now, but at times it turns of automatically and goes into the apple logo screen before starting up again.

I'm not sure what I did wrong. Is the battery too loose? Should it be closer to the connector? Like almost completely to the right side? I kinda messed up placing the strips and had leftover strip at the bottom of the battery. I wasn't sure what to do with it and I just crumbled it and left it tucked at the base of the battery. Any help would be awesome.