CompletionException intermittently seen from transactions

Performer specific validation failure: Hook dropped (raised async so could have been in an earlier test): java.util.concurrent.CompletionException: com.couchbase.client.core.error.DocumentNotFoundException: Document with the given id not found {"clientContext":{"txn.op":"ATR::getAtrWithUpToDateCas"},"completed":true,"coreId":"0x9458e5e20000004e","idempotent":true,"lastChannelId":"9458E5E20000004E/00000000A93230C7","lastDispatchedFrom":"172.18.0.4:49800","lastDispatchedTo":"172.23.111.128:11210","requestId":133233,"requestType":"SubdocGetRequest","retried":0,"service":{"bucket":"secondTestBucket","collection":"_default","documentId":"<ud>_txn:atr-13-#129e</ud>","errorCode":{"description":"Not Found","name":"KEY_ENOENT"},"opaque":"0x1fe72","scope":"_default","type":"kv","vbucket":13},"status":"NOT_FOUND","timeoutMs":2500,"timings":{"dispatchMicros":3858,"totalDispatchMicros":3858,"totalServerMicros":0,"serverMicros":0}} cause: com.couchbase.client.core.error.DocumentNotFoundException: Document with the given id not found {"clientContext":{"txn.op":"ATR::getAtrWithUpToDateCas"},"completed":true,"coreId":"0x9458e5e20000004e","idempotent":true,"lastChannelId":"9458E5E20000004E/00000000A93230C7","lastDispatchedFrom":"172.18.0.4:49800","lastDispatchedTo":"172.23.111.128:11210","requestId":133233,"requestType":"SubdocGetRequest","retried":0,"service":{"bucket":"secondTestBucket","collection":"_default","documentId":"<ud>_txn:atr-13-#129e</ud>","errorCode":{"description":"Not Found","name":"KEY_ENOENT"},"opaque":"0x1fe72","scope":"_default","type":"kv","vbucket":13},"status":"NOT_FOUND","timeoutMs":2500,"timings":{"dispatchMicros":3858,"totalDispatchMicros":3858,"totalServerMicros":0,"totalMicros":3967,"serverMicros":0}}