Premiere 2020: Audio & video don't sync after export

[coccinelle13]

I'm trying to put a couple of videos together that I recorded on my iPhone 7 (audio was also recorded by iPhone internally). The issue is, I am editing my videos in Premiere, and everything looks good, no issues whatsoever. Then I try to export it, and the file I end up with has an audio & video mismatch. 

My workflow is to use the razor tool to cut out the segments of video & audio (both are cut together, audio and video simultaneously, they are linked), and dragging  the second part of the video back to the end of the first, so that it is seamless. I am using .mov files and am editing on my macOS Catalina 10.15.7 using Premiere Pro 2020. 

Here are the export settings that I have always been using and have worked for me until today: I'm exporting it as a .mp4 file using the setting format H.264, and preset YouTube 720p HD. Export Video and Export Audio are both checked, frame rate is the suggested (grayed out) 23.976, checked 'render at maximum depth', bitrate encoding 'VBR, 2 pass', target & max bitrate '32', checked 'use maximum render quality'. 

While I am far from being a Premiere expert, I have used this specific workflow quite often and it has never given me any problems, not sure which of the elements is different this time that is giving me a hard time, nothing I am aware of. I tried playing around a bit by trying out different frame rates, still the same result. Thank you for your time in helping me out with this issue, really appreciated!

[coccinelle13]

One aspect I forgot to add, not sure if it's relevant, I increased the speed of all videos to 115% (with settings as shown in screenshot below). Again, that is something that I always do and never caused me problems so far, but I just wanted to have mentioned it since it is part of my workflow.

[coccinelle13]

A few things I have tried since posting:

• Used HandBrake to change the frame rate to 29.97 and constant frame rate in the hope it might solve the issue (screenshot attached), but it made no difference. Video and audio still out of sync
• Based on other people's experiences, I tried to play around with export settings, and chose MPEG4 as well as HEVC instead of H.264, still the same issue after export.

What stumbles me the most is that it is so apparent in this video, and I have done 20 videos like these (all shot with my iPhone, all using the same settings) and this issue never came up. Any help would be appreciated.