Thank you. I am afraid I have some bad news.
1) Just because it is not standard or may be excessive does not mean that the clause would be voided. It is in the contract and signed by both parties. You agreed to it.
2) Just because they have not required it in the past does not mean that they cannot now. Unless you have proof that they decided never to demand this clause be enforced in writing, then they can decide to enforce the clause now.
So yes, if it is in the contract, they can enforce it. Even if they have not in the past, and even if it is a bit excessive for the business.
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