6 node SHC. SHC complains with this error from time to time.
KV Store has changed status to failed. _id field value of 256 is out of range.
You might open a case on splunk support for that.
What Splunk Version are you running btw?
Certainly something with the monogdb (kvstore):
https://github.com/cvallance/mongo-k8s-sidecar/issues/77
All the best,
Björn
Splunk enterprise v7.0.2