uis2sdk problem

Hi, I'm having problems getting a uis2 plugin to work here. But first need to complain that in addition to being way outdated, this SDK is virtually impossible to locate; without help from archive.org I would never have found it.

Then the problem at hand: When reducing the example to a minimal skeleton (sourcefiles posted below) and setting a uis2-button action to  "Dll button using image":

• the button shows only in WindowBlinds/SkinStudio own windows borders, not on other windows borders.
• when pressing the button on WindowsBlinds window I get the beep on release, but after the beep I get a busy-pointer for about two seconds and then the window closes.

Edit: I'm using Visual Studio 2015 (v140) and Windows 10 FastRing Build 18305.rs_prerelease.181213-2133

wbplug.c:

/*
 
	WindowBlinds UIS2 Dll Plugin DEMO v1.1
 
	© 1999 Stardock Systems, Inc
 
 
	All this code is copyright and should not be used for ANY other purpose other
	than making a UIS2 plugin for use with WindowBlinds.
 
 
	This plugin is a clock which can be embedded into the titlebar
	It has been designed to only show when the item is active.
 
 
*/
 
#include <windows.h>
#include <wingdi.h>
#include <stdio.h>
#include <time.h>
 
 
BOOL APIENTRY DllMain(PVOID hModule, ULONG ulReason, PCONTEXT pctx)
{
 
 
	if (ulReason == DLL_PROCESS_ATTACH)
	{
 
		return TRUE;
 
	}
}
 
 
 
BOOL WBDrawMulti(HWND hWnd, HDC DC, RECT* r, int state, BOOL active, int button)
{
 
	/*
 
	hWnd = Handle to window
	DC = Handle to Device Context
	r = Dimensions of item
	state = > 0 then its pressed, else not pressed
	active = This is TRUE when the window is active and FALSE when inactive
 
	*/
 
	return TRUE;
}
 
BOOL WBPress (HWND hWnd, int x, int y, int state)
{
 
	// x & y are the position of the pointer
	// best to ignore them - For future use
 
	// The user has clicked on the button.  It has not yet been released
 
	return TRUE;
}
 
BOOL WBRelease (HWND hWnd, int x, int y, int state)
{
 
	// x & y are the position of the pointer
	// best to ignore them - For future use
 
	// The user has clicked on the button.  Button released while the pointer is over item
	// So item has been clicked
 
	// We shall beep just to indicate something
 
	Beep(1000,500);
 
	return TRUE;
}
 
BOOL WBQuery (HWND hWnd)
{
 
	// This function is for future use
 
	// For when we support timers etc
 
	return FALSE;
}

plugin.def:

LIBRARY plugin
 
DESCRIPTION 'WindowBlinds Titlebar Plugin Dll'
 
EXETYPE WINDOWS
 
EXPORTS
 
	WBDrawMulti @1
	WBPress @2
	WBRelease @3
	WBQuery @4