I did this

curl -K list_of_urls

list_of_urls:

--compressed
--parallel
--parallel-max 5
--parallel-immediate
--retry 5
--retry-delay 1
-H "some: header"

-o "out/1"
url=https://url.with.occasional/error.429
-o "out/2"
url=https://url.with.occasional/error.429
-o "out/3"
url=https://url.with.occasional/error.429
...
-o "out/100"
url=https://url.with.occasional/error.429

I tried without --parallel-immediate and without --compressed and setting --retry before each url, same result.
I also tried with --fail (learned from last issue 😉)
If I remove --retry it doesn't hang but well the ones who failed failed 😄

I expected the following

Receive files with content after trying again if it failed with 429 (or any of the other HTTP errors)

What happens

curl hangs and the progress meter counts up but nothing happens, the failed files stay at 0 bytes.
sometimes 15 files are created sometimes 12 sometimes ... can't see a pattern there.

curl/libcurl version

current master branch

[curl -V output]
curl 7.73.0-DEV (x86_64-pc-linux-gnu) libcurl/7.73.0-DEV OpenSSL/1.1.1f zlib/1.2.11
Release-Date: [unreleased]
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
Features: AsynchDNS HTTPS-proxy IPv6 Largefile libz NTLM NTLM_WB SSL TLS-SRP UnixSockets

fails on 7.68.0 in the same/similar way

operating system

Linux xxxYYYzzz 5.7.12-050712-generic SMP x86_64 x86_64 x86_64 GNU/Linux

same result with kernel 5.4.0