Hi Freek Willem,
A sudden crash can also be caused by network latency. I saw this happen on AX4.0 in the past at two implementations.
Check also if the AOS server is connected by using ip addresses in stead of machine names. If you are using machine names, due to network latency the ip address cannot be resolved in time by the DNS and AX can crash as well.
So check the suggestions of Tommy and this one.