Unexpected replacing

[storenth]

Trying these while processing path-queries with unexpected output.
First case:

echo "?set_city=%D0%91%D0%B0%D0%BB%D0%B0%D1%88%D0%B8%D1%85%D0%B0&back_url=/" | qsreplace http://127.0.0.1:8080

Out:

?back_url=http%3A%2F%2F127.0.0.1%3A8080&set_city=http%3A%2F%2F127.0.0.1%3A8080

Second case:

echo "/?set_city=back_url="  | qsreplace http://127.0.0.1:8080

Out:

/?set_city=http%3A%2F%2F127.0.0.1%3A8080

System: Mac Big Sur (11.2.1)

[storenth]

One more case:

▶ echo "Binary%20file%20/Users/storenth/lazytargets/example.com/recon-21-06-25_22-11-03/page-fetched/gpms-test.example.com/PragmataMedium.66f9722eccf3f5540174.ttf%20matches" | qsreplace -a

Binary%20file%20/Users/storenth/lazytargets/example.com/recon-21-06-25_22-11-03/page-fetched/gpms-test.example.com/PragmataMedium.66f9722eccf3f5540174.ttf%20matches