Can you reduce the code to a few lines and post them? I fear it's impossible for us to reproduce the described behaviour.

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use utf8;

my $string = qq(issue: "Problém s\N{NO-BREAK SPACE}odesláním");

binmode *STDOUT, ':encoding(UTF-8)';
say $string;
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