Thank you for reporting, we're working on a more robust backup system long term which should hopefully address save corruption. In the short term if you are having issues with network stability there are some things both you and the host can try to mitigate this such as adding the game as an exception to antivirus and firewalls, making sure you're on ethernet connection instead of wifi, and try to enable the "Network Workaround" setting in game to see if that helps. If the host does not have port forwarding set up we would recommend them doing that as well. Other suggestions I've heard would be to make sure your OS is up to date, reducing background programs, and disable any sort of network boosting programs.
On the other hand, if the game is crashing that sounds like a different issue, see below on how to file a bug report. We'll likely need logs for that.