I've been bothered a while by an annoying bug in Tribblix - Python applications couldn't open https connections in non-blocking mode. Which hindered access to S3 and Backblaze, for example.
Finally worked it out yesterday. Openssl needed to be built with -D_REENTRANT in order to enable per-thread errno so it catches failures and handles them correctly. That ought to have been the case anyway, but something was dropping it, so I needed to be explicit.