Those failed to store... messages have a high correlation with Cassandra problems. They are basically indicative that Acquisition did all of its work to obtain and process the data, but the Server is telling Acq that it was unable to store the data to complete the action so the performance poll functionally failed as the data had no where to go.
There are some Cassandra problems that only impact 1-n datasources, whereas there can also be systemic Cassandra problems where all datasources' performance packages fail with similar insertion messages.
Systemic Cassandra problems tend to occur on systems that are undersized, or have virtual memory problems due to small, fixed sized Windows paging files. We strongly recommend that OCI servers have paging files set to Windows managed sizing.
It sounds like you may be experiencing one of the 1-n problems, but I'd like to see a bit more.
If this OCI instance is sending OCI ASUP, could you PM me the site name?
Has some cassandra-client.log files. If you zip them up, and email them to me, I can take a look. However, there is a chance that root cause or when the problem started won't be captured, as these logs can roll over on large systems