Annotating files with ffmpeg and concatenating problem

Question

I annotate a bunch of files with:

ffmpeg -i migrant.mp4 -vf "drawtext=text='Migrant':fontcolor=white:x=100:y=100:font=Arial:fontsize=50" -codec:a copy migrant_test.mp4

I then concatenate them with:

ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp4

I get errors during concatenating and the output has lots of problems.

If I concatenate the original files, there is no problem in the output