このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
sqs message not deleted
対処
関連リンク
SQS Messages Not Deleting - Stack Overflow
https://stackoverflow.com/questions/10194293/sqs-messages-not-deleting
aws sqs lambda: messages not re-appearing
https://stackoverflow.com/questions/52041726/aws-sqs-lambda-messages-not-re-appearing
Delete SQS messages only without deleting the underlying S3 ...
https://stackoverflow.com/questions/39458929/delete-sqs-messages-only-without-deleting-the-underlyin・・・
AWS-SDK: SQS How identify messages that were not deleted ...
https://stackoverflow.com/questions/38405181/aws-sdk-sqs-how-identify-messages-that-were-not-deleted・・・
SQS Messages never gets removed/deleted after script run
https://stackoverflow.com/questions/24259010/sqs-messages-never-gets-removed-deleted-after-script-ru・・・
Tutorial: Receiving and Deleting a Message from an Amazon SQS ...
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-receive-delete-messag・・・
DeleteMessage - Amazon Simple Queue Service - AWS Documentation
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_DeleteMessage.html
Amazon SQS Visibility Timeout - Amazon Simple Queue Service
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-visibility-timeout.ht・・・
Inflight Messages
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-visibility-timeout.ht・・・
Setting the Visibility Timeout
https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-visibility-timeout.ht・・・