APS Design Automation 2026 Update to .NET Core Add-In Save/Update Failure

I'm having difficulty trying to update our 2025 .NET Framework version to 2026 .NET Core.

I started with my own solution receiving these errors, then switched over to start from scratch using the updated DesignAutomationTest .NET Core template with the same results.

Locally, I'm able to run and debug without issue, but once the add-in has been deployed and being called it fails only on certain parameters. In the current scenario, we have a railing model with parameters that the user can adjust.

{
    "RailHeight": "75",
    "RailLength": "34",
    "Material": "Steel",
    "Duty": "Heavy",
    "Paint": "Red",
    "BottomRailStyle": "Plate"
}

When I change all the values except for the "BottomRailStyle", everything runs without issue. Once I change the "BottomRailStyle" value from "Plate" to "Rail", the add-in errors out when trying to update/save the file.

Error: 0 : [SampleAutomation] Document update/save failed: Unspecified error (0x80004005 (E_FAIL))

Error: 0 : [SampleAutomation] Processing failed. System.Runtime.InteropServices.COMException (0x80004005): Unspecified error (0x80004005 (E_FAIL)) at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams) at System.RuntimeType.ForwardCallToInvokeMember(String memberName, BindingFlags flags, Object target, Object[] aArgs, Boolean[] aArgsIsByRef, Int32[] aArgsWrapperTypes, Type[] aArgsTypes, Type retType) at Inventor._DocumentClass.Update2(Boolean AcceptErrorsAndContinue) at UpdateUserParametersPlugin.SampleAutomation.Run(Document placeholder) in C:\Users\m.r\source\repos\DesignAutomationTest\DesignAutomationTest\DesignAutomationTestPlugin\SampleAutomation.cs:line 400

Sometimes the error below appears instead when trying to set the parameters:

error    The set senddmp exe does not exist, C:\DARoot\AcesRoot\30.00\coreEngine\Exe\CER\senddmp.exe
error    Cannot find upi exe at C:\DARoot\AcesRoot\30.00\coreEngine\Exe\Inventor Server\Bin\upi.exe or ..\upi.exe
error    UPI Config file C:\DARoot\AcesRoot\30.00\coreEngine\Exe\upi\upiconfig.xml does not exist
error    failed to launch  5392 2326167213728, cannot launch  5392 2326167213728, 87
[SBXMSG] The process 5392 ended.

This also happens with the Screwdriver model when I try to change the "Bit Type" value. All other parameters don't cause any issues.

This is where it fails in the code:

Parameters docParams = oComponentDef.Parameters;

foreach (KeyValuePair<string, string> entry in parameters)
{
    var paramName = entry.Key;
    var paramValue = entry.Value;

    logger.Info($"========== Processing param: {paramName} = {paramValue} ==========");

    // Isolate each parameter in its own try-catch
    try
    {
        // Try to set the parameter
        ChangeParam(docParams, paramName, paramValue);

        logger.Info($"========== Completed {paramName} ==========");

    }
    catch (Exception ex)
    {
        logger.Error($"========== FAILED {paramName} ==========");
        logger.Error($"Critical error setting {paramName}: {ex.Message}");
        throw;

    }
}

logger.Info("All parameters processed");

try
{
    logger.Info("Updating document after parameter changes...");
    doc.Update2(true);

    logger.Info("Saving document after parameter changes...");
    doc.Save2(true);

    logger.Info("Document updated and saved successfully");

}
catch (Exception ex)
{
    logger.Error($"Document update/save failed: {ex.Message}");
    throw;
}

Any insight or guidance would be greatly appreciated. Thanks in advance for your help.

Kind regards,
Marvin Ramirez