Pre-empting your reply - this should only be likely to occur if your cluster was inconsistent when you removed the index, if your cluster was full sf/rf then you may have other underlying issues.
If this is a production cluster, you may wish to consult with Splunk support - but if your cluster is expendable (and with all the normal caveats about taking advice from some random guy on the internet)
Run this query to get a list of buckets which have failed to replicate properly:
Export that as a csv (confirming all the buckets are ones you want to remove)
Depending on the total number of buckets you can either remove them one by one using:
curl -k -u admin:changeme -X POST "https://clusterMAaterAddress:8089/services/cluster/master/buckets/akamilogs~xxxx~xxxxxxxxx-xxxx-xxxxx-xxxxx-xxxxxxxxx/remove_all"
Or this script will delete the lot (run the script in the same folder as the csv)
cat bad_buckets.csv | while read bucket
curl -k -u admin:changeme -X POST "https://clusterMAaterAddress:8089/services/cluster/master/buckets/$bucket/remove_all"
You would be wise to test this by removing one or two buckets, and confirming that the errors stop for those bids. Also, I have typed this on a train with no access to splunk, so it has not been tested, so please take every precaution - peer review / backups / mother on speed dial...