[Answer]
This issue is happening due to the timing of dashboard refresh and pdf export.
When a dashboard is due to refresh, it calls cancel of all the dashboard search jobs and request for a fresh run.
This issue happens when refresh kicks while pdfgen is still rendering the searches.
This is a limitation to PDF generation. (We'll update the document soon.)
https://docs.splunk.com/Documentation/Splunk/7.2.3/Viz/DashboardPDFs
[Workaround]
Change the refresh time to a bigger value (the issue still happens, but the frequency becomes lesser.)
Disable the refresh time and change the search to real-time search
*Please note real-time search consumes more resources.
https://docs.splunk.com/Documentation/Splunk/7.2.3/Search/Aboutrealtimesearches
[Behavior]
dashboard
0. Dashboard is updated.
1. Wait for the refresh time.
2. The refresh time has passed.
3. Change the status of searches to cancel. (To prevent Splunk having 2 valid search results.)
4. Request a new search, and return to 0.
pdfgen
a. Find all Search IDs for all searches.
b. Render the search results using data in the corresponding folders under dispatch.
c. PDF is created.
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