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Poll Interval is changed to 1h and continues to work fine:
Now with 5m:
Conclusion
If a Poll Interval of a service that is 1m, 2m, 10m, 15m is modified to 30m or more, the service graphs are stopped. If the Poll Interval is returned to the initial value (less than 30m), the graphs recover but a gap is observed at the time when it was 30m or more.
If a Poll Interval of a service that is 30m is modified to 60m, and then to 5m, the service graphs continue to work fine.
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