I have to apologize - you reported this problem as a bug in WWW::Mechanize::Chrome and I rejected that bug because I could not reproduce it. But it is an actual bug. With your posted code above, I can easily reproduce the issue and the problem is that the code does not cope with a Page.navigatedWithinDocument element at all.

I've added the following code to WWW::Mechanize::Chrome, which should fix that issue, or at least not crash anymore:

     } elsif ( my $res = $events{ 'Network.responseReceived' }) {
     #warn "Network.responseReceived";
             $response = $self->httpResponseFromChromeResponse( $res )
+;
             $response->request( $request );
 
+    } elsif ( my $res = $events{ 'Page.navigatedWithinDocument' }) {
+        # A fake response, just in case anybody checks
+        $response = HTTP::Response->new(
+            200, # is 0 for files?!
+            "OK",
+            HTTP::Headers->new(),
+        );
+        $response->request( $request );
[download]

A new version of WWW::Mechanize::Chrome is just testing and then on its way onto CPAN.