[gentoo-user] locating non utf-8 characters

I'm using sql-ledger and while making backup it uses stardard gzip program:
$gzip = "gzip -S .gz";

The backup works with some dataset but one data set us giving me an
error while trying to perform backup:

Wide character in print at SL/AM.pm line 2044.
Content-Type: application/file; Content-Disposition: attachment;
filename=dataset_3-3.2.6-20201101.sql.gz
ãù&ü_1604265628.dataset_3-3.2.6-20201101.sqlÏ\Yo;ñ~œØ –

Since sql-ledger file are standard utf-8 files, I was thinking using:
 grep -axv '.*' file

would find all not utf-8 characters. And it did. I use "nano" to remove
them but I'm still getting the same error while performing backup.

Any ideas?

-- 
Thelma