FFMPEG start offset weirdness

Experiencing weird start offset issues when re-encoding a video with FFMPEG.

My original video:
Duration: 00:00:15.06, start: 0.000000, bitrate: 20464 kb/s

When I apply the below encoding settings...
ffmpeg -i in.mp4 -c:v libx264 -profile:v high -level 4.1 -b:v 7000k -c:a aac -b:a 192k -strict -2 -threads 0 -y out.mp4

...my output video looks like this:
Duration: 00:00:15.08, start: 0.021333, bitrate: 7345 kb/s