storeShardCheckpoint not catching ConditionalCheckFailedException

[dselman]

We are seeing logs like this every 10 seconds or so:

ConditionalCheckFailedException: The conditional request failed
at Request.extractError (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/protocol/json.js:51:27)
at Request.callListeners (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
at Request.emit (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
at Request.emit (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/request.js:683:14)
at Request.transition (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/request.js:22:10)
at AcceptorStateMachine.runTo (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/state_machine.js:14:12)
at /app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/state_machine.js:26:10
at Request.<anonymous> (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/request.js:38:9)
at Request.<anonymous> (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/request.js:685:12)
at Request.callListeners (/app/node_modules/lifion-kinesis/node_modules/aws-sdk/lib/sequential_executor.js:116:18)

I noticed that the call to storeShardCheckpoint is not protected by the same try/catch as the other calls, which swallows ConditionalCheckFailedException.

Note that we are running with useEnhancedFanOut=true.

Could this explain what we are seeing?