Hi Marnix,
This is likely the result from a configuration error, or the result of the JVM process being killed by an operating system OOM, or by a segmentation fault or something worse, if possible.
I found some documentation that might help to understand: https://world-test.mendix.com/display/howto40/Linux_Monitoring+using+Nagios
I think that the app is running out of memory and we might need to add some OS memory. Could you please create a ticket for this and add the mendix url's so that I can check this for you?
Thanks, Sultana Mir Customer support Engineer