Documentation for HTTP::Request::Common states:

If a $file is provided by no Content-Type header, then Content-Type and Content-Encoding will be filled in automatically with the values returned by LWP::MediaTypes::guess_media_type()

Maybe a module upgrade has changed the behaviour of LWP::MediaTypes::guess_media_type() to guess differently for .bin files. Try POSTing with the encoding set explicitly, like 'Content-Type'   => 'application/octet-stream'.

To investigate further, use LWP in debug mode as follows and observe the headers:

use LWP::UserAgent();
use LWP::ConsoleLogger::Easy qw( debug_ua );
use HTTP::CookieJar::LWP();

## Create browser object.
my $jar = HTTP::CookieJar::LWP->new;
my $ua  = LWP::UserAgent->new(
    keep_alive=>200,
    cookie_jar => $jar,
    protocols_allowed => ['http', 'https'],
    timeout => 60,
);
debug_ua($ua);
# etc.
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bw, bliako