iconv terminated by signal 7

I was running a little bash script on some text files:

find . -name "*.dat" -exec iconv --from-code='UTF-8' --to-code='ASCII//TRANSLIT' {} --output={} \;

My machine is a Ubuntu 14.04 LTS.

After a while, I found that like half of the data in the files disappeared; simply cut off in the middle of a line/word. It is the mysterious signal 7 or core dump (as I heard). The problem is somehow, when the files are too large. Some of my file have >60kB but iconv made them around 30kB.

What can I do about this? Is this a bug? Is there a workaround? Is there any other convenient way to transliterate diacritics?