Asterisk removes wav files

Some of the records of calls are automatically deleted asterisk. Launched in cron’e script that every minute creates a reference to the record. Recording audio in Asterisk - stream (a file is created and appended to it). The script creates a link to the recording. After hangup this record miraculously disappears. Although the report in asteriskcdrdb database has a call and duration. It is only with uncompressed wav, not all records (see screenshot).
What is the reason?