Hi Steven,
from the graph it seems like the query is stopped by the standard timeout for the Check_MK service after 60 seconds.
Depending on which edition of Checkmk you use, this timeout can be changed differently.
In the free Raw Edition / when using the Nagios Core:
Edit the file ~/etc/nagios/nagios.cfg in your Site-directory and add a line with “service_check_timeout=90” where the number represents the amount of seconds:
# ~/etc/nagios/nagios.cfg
service_check_timeout=90
After this a cmk -R is needed to reload the Nagios core.
Be aware that this is then applicable for every Active Check on your site. This can increase the CPU load of your Checkmk Server.
In the other editions / when using the Checkmk Micro Core:
There is a rule “Service check timeout (Micro Core)”, with it you can increase the timeout for specific Hosts and Active Checks like the Check_MK Service.
Hope this helps 
Cheers,
Leon