C# Elasticsearch 8.0.3+ 400 Bad Request media_type_header_exception

Elastic Stack Elasticsearch
,
5

Tried some more things, only the GetEntryAssembly locations is returning anything, but that is NOT 'our' DLL. So cannot even get our own version in this way.

GetExecutingAssembly location: 
Error GetExecutingAssembly version: The path is not of a legal form.

GetEntryAssembly location: D:\SvcFab\***\ConnectExecutorActor.exe
GetEntryAssembly version: 1.0.0

GetCallingAssembly location: 
Error GetCallingAssembly version: The path is not of a legal form.

ElasticsearchClient assembly location: 
Error getting assembly version: The path is not of a legal form.

Code:

try
{
	Assembly executingAssembly = Assembly.GetExecutingAssembly();
	string executingAssemblyLocation = executingAssembly.Location;
	Context.Log(LogLevel.Error, $"GetExecutingAssembly location: {executingAssemblyLocation}");
	string executingAssemblyVersion = FileVersionInfo.GetVersionInfo(executingAssemblyLocation)?.ProductVersion;
	Context.Log(LogLevel.Error, $"GetExecutingAssembly version: {executingAssemblyVersion}");
}
catch (Exception ex)
{
	Context.Log(LogLevel.Error, $"Error GetExecutingAssembly version: {ex.Message}");
}

try
{
	Assembly entryAssembly = Assembly.GetEntryAssembly();
	string entryAssemblyLocation = entryAssembly.Location;
	Context.Log(LogLevel.Error, $"GetEntryAssembly location: {entryAssemblyLocation}");
	string entryAssemblyVersion = FileVersionInfo.GetVersionInfo(entryAssemblyLocation)?.ProductVersion;
	Context.Log(LogLevel.Error, $"GetEntryAssembly version: {entryAssemblyVersion}");
}
catch (Exception ex)
{
	Context.Log(LogLevel.Error, $"Error GetEntryAssembly version: {ex.Message}");
}

try
{
	Assembly callingAssembly = Assembly.GetCallingAssembly();
	string callingAssemblyLocation = callingAssembly.Location;
	Context.Log(LogLevel.Error, $"GetCallingAssembly location: {callingAssemblyLocation}");
	string callingAssemblyVersion = FileVersionInfo.GetVersionInfo(callingAssemblyLocation)?.ProductVersion;
	Context.Log(LogLevel.Error, $"GetCallingAssembly version: {callingAssemblyVersion}");
}
catch (Exception ex)
{
	Context.Log(LogLevel.Error, $"Error GetCallingAssembly version: {ex.Message}");
}

try
{
	Assembly elasticAssembly = typeof(ElasticsearchClient).GetTypeInfo().Assembly;

	if (elasticAssembly is null)
	{
		Context.Log(LogLevel.Error, $"ElasticsearchClient assembly: NULL");
	}

	string elasticLocation = elasticAssembly.Location;
	Context.Log(LogLevel.Error, $"ElasticsearchClient assembly location: {elasticLocation}");

	string elasticVersion = FileVersionInfo.GetVersionInfo(elasticLocation)?.ProductVersion;
	Context.Log(LogLevel.Error, $"ElasticsearchClient assembly version: {elasticVersion}");
}
catch (Exception ex)
{
	Context.Log(LogLevel.Error, $"Error GetCallingAssembly version: {ex.Message}");
}

try
{
	Assembly elastic2Assembly = typeof(ElasticsearchClient).Assembly;

	if (elastic2Assembly is null)
	{
		Context.Log(LogLevel.Error, $"elastic2searchClient assembly: NULL");
	}

	string elastic2Location = elastic2Assembly.Location;
	Context.Log(LogLevel.Error, $"elastic2searchClient assembly location: {elastic2Location}");

	string elastic2Version = FileVersionInfo.GetVersionInfo(elastic2Location)?.ProductVersion;
	Context.Log(LogLevel.Error, $"elastic2searchClient assembly version: {elastic2Version}");
}
catch (Exception ex)
{
	Context.Log(LogLevel.Error, $"Error GetCallingAssembly version: {ex.Message}");
}