I switched encoding from aac to libfdk_aac due to qaulity issues. I noticed with the new encoding a small part of the audio file will be cut in the beginning. I tested this with multiple files. This is the command i am using:
ffmpeg -y -noaccurate_seek -i file.mp3 -b:a 260k -c:a libfdk_aac -vn -movflags +faststart output.m4a
I tried different variations but alway ended up with cut file.
Here is the output of a wave editor