Error Validation of viewstate MAC failed but only on Chrome

I have my ASP.NET WebForms application set up to catch any and all errors and log them. Almost every day I get at least one of these errors:
Exception: System.Web.HttpException (0x80004005): Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. System.Web.UI.ViewStateException: Invalid viewstate. 
which sounds like a machine key error right? nope... machine key is generated and set up for that web app like it should be. The server version is IIS 7.5.
Now here's the odd thing, this error ONLY happens with google chrome. I do not get a single error from Safari, Internet Explorer or FireFox, only google chrome users.
I have the web app running as .NET 4.5 with the http target runtime set to 4.5 and the compiler set to 4.5 with request validation mode set to 4.0.
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