I cannot find any record of an official version 15.00.2327. Sometimes if a customer has a serious issue, MS Support will issue the customer a hotfix directly to a non-official version. But, I have never seen this kind of error due to a hotfix version and would not expect this kind of error. MS Support expects customers to update to the next CU when available to get the official supported version.
First, I would suggest you get the output from the customers server of SELECT @@VERSION.
Second, I would recommend they patch their server to a supported CU version.