We are seeing this here (at U of M). With 10.12, https file transfers of large files (think 2G or larger) are failing where the same files will transfer fine on 10.11.
We are hoping others who can test/see this will report it to Apple's Bug Reporter to raise awareness of the issue.
You can test this by putting a large (try 5G) empty .dmg on a site and then just running:
curl -O https://<url-to-file>
3 or 4 times and you will probably see that fail more often than not.
This has been seriously impacting us because many of the packages we deploy (or our NetBoot Images, or our OS installers) are failing to download from our https repository consistently.
We are hoping others that try this (and fail) will open additional bug reports -- especially if you have an AppleCare contract.
Thanks!
