Steps to reproduce:
1. There is no reproduction project for this issue
Actual Result: due to missing CURLOPT_SEEKFUNCTION, curl error 26 is caused on POST retry with reused connections
Expected Result: POST requests should transparently retry and succeed when a reused connection is closed by the server, rather than failing with curl error 26
Reproducible with according to the customer: 6000.3.14f1
Could not test locally on 6000.0.77f1, 6000.3.17f1, 6000.4.11f1, 6000.5.0f1, 6000.6.0a7 due to missing reproduction project/scenario
Testing Environment: Windows 11
Not reproducible on: no other environment tested
Notes:
-Customer confirmed that this is happening with POSTs that don't use multi-pass authentication, so they are wondering if the problem is with connection reuse
-Discussion thread: https://discussions.unity.com/t/curl-error-65-neccessary-data-rewind-wasnt-possible/849943/23