File data loss in stream event


I’m sorry to bother you.
During using Zeek I met some problem. Could you help me?

I found a bro package named credit-card-exposure(link), and imitated the bro script in this package for detect some sensitive info.
Part of the code is as follows

I printed the fields named seen_bytes and total_bytes of all the files, and found that many data of files have not entered the handler of stream event. I can also find in files.log, the seen_bytes was far less than total_bytes.
what can I do to solve this problem?

Yours respectfully