Have you tried launching iTunes as the administrator?
I refuse to run iTunes with escalated privileges tokens and i see no point in doing so since restoring old version of iTunes fixes the issue with no other changes to environment, so it is definitely a problem with code in new version. Additionally i can verify that iTunes has permissions to access library. Can you provide any reason why it would require escalation tokens from Windows? Even if it does, it is still a bug.
Aha, I've just recalled a similar instance that was resolved by first disabling the firewall and then tweaking the settings of it so iTunes would then run without error. Do you have a firewall in place?
Yes i'm using Windows Firewall (with Advanced Security since i'm running Pro version of Windows) however again - old version of iTunes was working fine and is still working fine after restoring it so i see no reason why it would be an issue - i can additionally confirm that rule pointing to 'C:\Program Files\iTunes\iTunes.exe' exists in Inbound store allowing iTunes for any inbound connections on all network security profiles and was configured upon installation of iTunes, it has however nothing to do with iCloud Music Library as it is using HTTP connections to Apple servers to upload files and would fall under Outbound store which is configured per default to allow any connection.
As additional information i can say that crash is happening in-between iCloud Music Library upload session, after initial metadata of albums and playlist (such as names) was uploaded and before actual files are being transferred to Apple servers - do note that this causes in 1 of 3 times a situation where upon opening iTunes again, duplicated albums or playlists are visible.
Additionally, changing metadata such as creating or removing playlist, removing songs, changing album or song info works fine - the issue shows up only when iTunes tries to upload new track.