To which server did you connect in the game for multiplayer? always the same?
Which game title are you using exactly?
Because there is one thing you should definitely be aware of:
With the new update, a new title was introduced, "TrackMania²" title, that combines all previously existing TrackMania² titles together (Canyon, Stadium and Valley).
This new title also features the possibility to have a server that switches between maps of the different titles Canyon, Stadium and Valley without need of exiting a title and restarting another one.
Additionally, Canyon and Valley tracks can now use also the cars of the other titles.
Now if you don't own all the three TM² titles, but if you're still joining such a "envi-mix" server (this is unfortunately possible at the moment), it will somehow throw you out at the change to a map your ManiaPlanet installation is not supporting.
They also have added a demo countdown, where you can play for some time on a track (20 minutes per title per day).
This might also cause a kick of a server then.
Agreed that this is not optimal now, and causes some frustration.
Besides this there are quite a few different other possible issues for the crashes some users are experiencing.
One of them is a mismatch of the server controller software (developped by Nadeo, but also different tools by the community) and the most actual version of the dedicated server software (only developpled by Nadeo).
Those issues are currently being investigated and successively fixed, but it takes time.
Some servers have issues with certain maps, this means the admins have to look into the server logs and see when players disconnected unattendedly, and try to pinpoint which map is bad, and then remove it from the list.
And another user reported that the usage of antialiasing was causing constant crashes (unconfirmed by others up to now).
The developpers actually know that it is a bit of a unlucky situation with the current update, but you can be sure that they will do everything possible to fix those crashes. It takes a bit since it is not always clear where the crashes are coming from.
Please be patient and don't get too angry
