push fails on one server but not another-cIisCustomHeaders

I have two server dev-ap1 and dev-ap2 - everything looks fine on the ap2 server

Cannot convert value "System.Object[]" to type "System.Xml.XmlDocument". Error: "The specified node cannot be inserted as the valid child of 
this node, because the specified node is the wrong type."
    + CategoryInfo          : InvalidArgument: (:) [], CimException
    + FullyQualifiedErrorId : InvalidCastToXmlDocument
    + PSComputerName        : dev-AP1
The PowerShell DSC resource CMP_cIisCustomHeaders threw one or more non-terminating errors while running the Test-TargetResource 
functionality. These errors are logged to the ETW channel called Microsoft-Windows-DSC/Operational. Refer to this channel for more details.
    + CategoryInfo          : InvalidOperation: (:) [], CimException
    + FullyQualifiedErrorId : NonTerminatingErrorFromProvider
    + PSComputerName        : dev-AP1
The SendConfigurationApply function did not succeed.
    + CategoryInfo          : NotSpecified: (root/Microsoft/...gurationManager:String) [], CimException
    + FullyQualifiedErrorId : MI RESULT 1
    + PSComputerName        : dev-AP1

The error suggests that the resource is modifying an XML file, and that on the failing server, the file is not in the same condition as on the successful server. On the failing server, the XML modification is invalid. Honestly, though, that’s all I can tell you solely from looking at an error message. Without sitting down and comparing both XML documents and examining the code of the resource - which is a big task - I can’t give you any more detail.

But I’d start by comparing the two XML files prior to the LCM running, to see if they’re identical or not.

I would also check you have the same level of .net framework on both servers