My Dad’s Ethereum transaction is pending for 11 hrs

it this normal ?

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https://etherscan.io/tx/0x6599c251b3d44a731f29f5c42b8090f19bc9028863ec2a14792cd3546997dd2d

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This was relatively a simple transaction. He just wanted to transfer ETH from 1 exchange to another (both belonging to him). He did it many times and all of them (apart from this) went smoothly.

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This transaction for some reason has been stuck for 11 hour……. Just want to know, will it eventually be cleared or should my dad do something for it to be expedited ?