Resolve Error: Cannot Enable Collaboration | Clients can't see each other via Wireguard

My friend and I get this error by DVR (DaVinci Resolve) when connecting to a project:


One person can connect to a project without any issues but the second person will get this error. Has BMD made some changes to DVR and now it's not fooled by the VPN approach anymore?

What we've set up:

- Resolve Collaboration Server in W10 VM on my home server.
- Port-forwarded the respective ports and pointed a domain to my router.
- Created the necessary PostgreSQL databases and users (connected to them on the project server via the default user `postgres`.
- Successfully authenticated all clients with the server via the URL.
- Exported the Wireguard configuration, opened the tunnel on the server, and activated the connection on the clients.
- Successfully added our databases on the clients in the Resolve Project Manager by using our usernames and the server's Wireguard IP of `9.0.0.1`.
- Enabled sharing for the databases on the server, and enabled collaboration for the projects we want to collaborate on.

Our systems:

- Windows 10 20H2 (R9 3900, GTX 1660S, 30Mb/s upload to collaborator)
- Windows 10 20H2 (old 4 Thread-CPU, onboard-GPU)
- both DVR 17.3.1 (one Studio, one Free)

*Media is stored locally on both of our machines and made to have the same path. Everything is live-synced via NextCloud.*

[server_log.txt](https://github.com/jonnyhyman/ResolveCollaboration/files/7195170/server_log.txt)