Trying to call functions crashes app

I am trying to call exported functions from my C++ program. However, it crashes/freezes on call.

I have setup a few test methods to check if the dll works at all and it already crashes on the very first test which is one without a signature.

code snippet .NET Framwork 4.7.2

[DllExport("TestFunc1", CallingConvention.StdCall)]
[return: MarshalAs(UnmanagedType.LPUTF8Str)]
public static string TestFunc1() {
    return string.Empty;
}

In C++:

// .h
    extern "C" {
        typedef char* (__cdecl *exTestFunc1)();
    }
    class DllMngr
    {
        public:
            char* testFunc1();
        private:
            HINSTANCE   m_dllHandle;
            exTestFunc1 m_exTestFunc1;
    }

// .cpp
    m_exTestFunc1 =reinterpret_cast<exTestFunc1>(fetchMethodHandle("TestFunc1", l_result));

    char* DllMngr::testFunc1() {
        if (!m_dllHandle) {
            return "Dll not loaded.";
        }
        return m_exTestFunc1();
    }

// call
   char* l_test1 = m_DllMngr->testFunc1();

I believe there might be some incompatibilities or the export settings are wrong. Do note that my dll handles are valid and my method handles are valid as well. Everything gets loaded correctly before trying to call it.

Any help would be appreciated.

The project I load the dll in is x86

. . .

The question is related to:

DllExport -version: 1.7.4.29858+c1cc52f

Copy-paste from Data tab:

Installed: True; 1.7.4+c1cc52f; invoked: 
Project type: Cs
Storage: ProjectFiles
Compiler.Platform: x86
Compiler.ordinalsBase: 1
Compiler.rSysObj: False
Compiler.ourILAsm: False
Compiler.customILAsm: 
Compiler.genExpLib: False
Compiler.peCheck: PeIl
Compiler.patches: None
PreProc.Type: None
PreProc.Cmd: 
PostProc.Type: None
PostProc.ProcEnv: $(SolutionPath);$(MSBuildThisFileFullPath)
PostProc.Cmd: 
SignAssembly: 
Identifier: 0F4F22C1-DBBF-4C9D-A96F-07554B0D45DF
Instance: C:\Program Files\Microsoft Visual Studio\2022\Professional\MSBuild\Current\Bin\amd64\MSBuild.exe
Project path: C:\_dev\lib_ext\crypto\GNUPG_Decrypt\0.0.1.0\Source\GNUPG_Decrypt.csproj
Action: Configure
PlatformTarget: x86
TargetFramework: 
TargetFrameworks: 
TargetFrameworkVersion: v4.7.2
RootNamespace: GNUPG_Decrypt
AssemblyName: GNUPG_Decrypt
MgrArgs: -packages libs -dxp-version actual -action Configure
MetaLib: tools\raw\lib\net20\DllExport.dll
MetaCor: tools\raw\lib\netstd\DllExport.dll
Proxy: 
StoragePath: .net.dllexport.targets
ddNS: GNUPG_Decrypt
ddNS max buffer: 500
UseCecil: True
intermediateFiles: False
timeout: 30000
Options: None
RootPath: C:\_dev\lib_ext\crypto\GNUPG_Decrypt\0.0.1.0\Source\
PkgPath: C:\_dev\lib_ext\crypto\GNUPG_Decrypt\0.0.1.0\Source\libs\\DllExport\
SlnFile: 
SlnDir: C:\_dev\lib_ext\crypto\GNUPG_Decrypt\0.0.1.0\Source\
DxpTarget: tools\net.r_eg.DllExport.targets
MsgGuiLevel: -1
LockIfError:

3F / DllExport

Trying to call functions crashes app #232