Playback Audio Out of Sync

First of all, I'm new to Resolve and this is my first project with it. Last week, we took an hour long video with a phone and phone automatically splitted it into two parts. So I started cutting and adding Fusions to the first video without any problems, but when I started part 2 it had a problem with audio and clip sync. First I checked whether the timeline frame rate and playback frame rate but they were both 30 FPS and both of the videos frame rate is 30 FPS. When I changed playback frame rate to 33 the audio sync problem in part 2 stopped, but in part 1 same problem started. So what may be causing this problem and how can I fix it?

Cell phones aren't good options for filmmaking.

https://www.blackmagicdesign.com/produc ... nemacamera

Jim is right. Smartphones are notorious for not keeping a constant speed. If you check it in MediaInfo's second page, you'll see that it has variable frame rate. Such a long recording with a smartphones is asking for trouble.

Get a real camera or sync it with dozens of manual cuts…