We have observed the error CURLE_SEND_FAIL_REWIND occurring during authentication. This error occurs when data that has already been sent to the authentication server needs to be resent, which can happen as part of some multi-pass authentication methods (source: https://curl.se/libcurl/c/CURLOPT_SEEKFUNCTION.html), but there is no seek/ioctl function set to allow rewinding to the data that needs to be sent. To fix this, we need to define a CURL_OPT_SEEKFUNCTION so that we can correctly rewind.