Studio not applying standard regex rules?

We are working on a large number of cshtml files for which we have created a Regex. However, we encountered issues where Studio's handling of a regex seems different from the standard. Here is an example:
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"Your External Learning request @(this.Model.ExternalLearningRequest.Number) to attend @(this.Model.ExternalLearningRequest.Name) from @(String.Format("{0:d}", this.Model.ExternalLearningRequest.StartDate)) to @(String.Format("{0:d}", this.Model.ExternalLearningRequest.EndDate)) has been approved by the @(this.Model.Employee.BusinessUnit) 2nd Level Approver."
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We need to obviously block all code segments and we are using the following regex:
@\([^)\r\n]*\)
When testing the regex - for example online on regex101.com and regexr.com -, it correctly identifies all instances. But when loading the string in Studio, using the same regex, the result looks like this:
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Your External Learning request ", this.Model.ExternalLearningRequest.EndDate)) has been approved by the  2nd Level Approver.
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Does anyone have a suggestion how to modify the Regex to work properly in Studio?