For my part i had big difficulties to join the server.
I had multiple times the message "Banned for cheat possible".
I think i needed around 15 attempts to join the server.
Maybe it was due to the big amounts of participants.
Then when i was driving on this track i had no problems of lag or anything.
I am using a software to use all my CPU Cores for GTR2 (i think it can help from some issues) and i also made change to the antialiasing/anisotropic settings with software "Nvidia Profile Inspector" which fixed for me issues with lag.
For those who interested i wrote a post about it there
https://www.koelschbierbude.de/component/
option,com_fireboard/func,view/Itemid,99/catid,63/
id,15790/
I am not really sure these advises would have helped for the issues there were in Melbourne but it costs nothing to advise them.
I don't really know if all the issues on this race was due to the mod, the track, the amount of participants or a little bit of everything.
Simple & Good idea from Fin to advise to reinstall the 4GB Patch.
I noticed Nilski98 had a "crashed game" just some seconds after asking for a "pit request" so it sounds a Pitstop issue for him, maybe it is a track problem as i had same kind of problem with pitstop in Baku & Zandvoort only.
It can be a hint...i don't know
For the "Banned for cheat possible" message maybe it would be good mainly for the new players on GTR2 to inform that it is necessary to insist sometimes lots times to join the server.