SQS FIFO Queue Not maintaing the order for same message group id.

One of the mechanisms that can break the order of messages in FIFQ queue is DLQ. Please see this documentation and notate the following:

Don’t use a dead-letter queue with a FIFO queue if you don’t want to break the exact order of messages or operations. For example, don’t use a dead-letter queue with instructions in an Edit Decision List (EDL) for a video editing suite, where changing the order of edits changes the context of subsequent edits.

https://aws.amazon.com/de/blogs/compute/using-amazon-sqs-dead-letter-queues-to-control-message-failure/