MaxScale uses microhttpd to implement the admin interface/REST API:
microhttpd allows an application to handle errors by setting an error handler by calling the MHD_set_panic_func function:
Function: void MHD_set_panic_func (MHD_PanicCallback cb, void *cls)
Set a handler for fatal errors.
function to call if MHD encounters a fatal internal error. If no handler was set explicitly, MHD will call abort.
closure argument for cb; the other arguments are the name of the source file, line number and a string describing the nature of the fatal error (which can be NULL)
MaxScale doesn't seem to currently do this, so microhttpd error messages are lost. This can make problems with the admin interface more difficult to debug.