Adding a variable to a class causes a WinRT originate error.

Question

I have a Clock class which causes my game to crash after I add the following line
public:
int FrameTimeTicks; // this line will cause the crash
the error message reads:
First-chance exception at 0x74B24598 (KernelBase.dll) in HH.exe: 0x40080201: WinRT originate error (parameters: 0x80000013, 0x0000001D, 0x02C3D5E0).
First-chance exception at 0x74B24598 in HH.exe: Microsoft C++ exception: Platform::ObjectDisposedException ^ at memory location 0x02C3DA80. HRESULT:0x80000013 The object has been closed.
WinRT information: The object has been closed.
The program '[8200] HH.exe' has exited with code 0 (0x0).
This is completely meaningless to me. It's a strange problem.
Edit: When i step through the program, a breakpoint on the first line of MainPage() isn't reached before the exception is thrown. I can put a breakpoint in Clock constructor which looks like this:
Clock::Clock()
QueryPerformanceFrequency(&frequency);
QueryPerformanceCounter(&pCountAppStart);
//FrameTimeTicks = {};
And it will be hit, when i step through from there, execution reaches the end of Clock(), goes to MainPage() open brace, but before it hits the first line I get "Source not available - Source information is missing from the debug information for this
module ..."
So has MainPage been disposed ?
Here is the Clock.h file:
#pragma once
#include <Windows.h>
#include <map>
#include "Debug.h"
using namespace std;
using namespace Platform;
using namespace Platform::Collections;
class Clock
public:
Clock();
int64 MarkIn();
int64 MarkOut();
//int FrameTimeTicks; // can't add these
//int FrameTimeMS = 0;
private:
LARGE_INTEGER frequency = {};
LARGE_INTEGER pCountAppStart = {};
LARGE_INTEGER pCountStt = {};
LARGE_INTEGER pCountEnd = {};
//int frameTimeTicks; // can't add these either
//int frameTimeMS;

Answer 1

So I think I have found the problem here, and I came to a fix by using Analyze > Run code analysis on solution. Something I've never used before. When i ran it, it gave me 3 issues, one of the issues was that I was using a byte* to pixel data after a
failed call to
IBufferByteAccess->Buffer(&pixels);
I don't know why the call is failing as I call it immediately after creating the WriteableBitmap, and then later in ClearBitmap. Also, the call result never returns a failure. But, nevertheless, by checking for the HRESULT and returning NULL if it fails,
then checking for NULL in the calling functions. The issue seems to have been resolved and I can add variables to my clock class.
I guess something weird was happening with memory.