ReadThroughCacheLookupCanceled is an error generated in the read through cache (which the index cache is based on). When a lookup request finishes successfully then it cancels all in progress lookups.

This error is happening because in the index cache the ReadThroughCacheLookupCanceled error is not being captured and retried.

This problem is not happening for the collection cache because the requests are being handled in the refresh, and there the convoy is being prevented.