kalsan Here is something you could try, though it may not work. When connected to that network, pull up the "Network details" screen and try switching from "per-connection randomized MAC" to "per-network".
If that by itself does not work, you could also try, in Vanadium: Settings, Privacy & security, Third-party cookies, Add site exception (if you can figure out which site) or Allow third-party cookies.
Please note that any of these changes will make you significantly more trackable! The fundamental issue is that you are hoping for your public-transit Wi-Fi to track you from one station to the next, which GrapheneOS is designed to avoid.
So if these changes do not solve the issue, arguably revert them. And even if they do solve the issue there is a fair case for reverting them!