cpp/cli interop dll breaks in visual studio 2015 - c++-cli

Question

I've been assigned the task of upgrading an old interop dll into visualstudio2015 with the v140 toolset.
I'm getting an odd access violation now.
Exception thrown at 0x000007fef7d3d95c (mscoreei.dll) in HostApp.exe:
0xC0000005: Access violation reading location 0xffffffffffffffff
Did anything change in cpp/cli from v110 to v140?
I can tell the error occurs when the methods are defined in a separate cpp instead of inline in the Foo.h. This work-around isn't possible since this is where I need to call managed objects.
Here is my attempt at reconstructing the outline of the code:
shared header IFoo.h
#ifdef DLL_EXPORTS
#define __API__ __declspec(dllexport)
#else
#define __API__ __declspec(dllimport)
#endif
class IFoo
{
public:
__API__ static IFoo* Create();
virtual void DoSomething()=0;
};
Foo.h
#include IFoo.h
class Foo : public IFoo
{
public:
Foo() { } // if inline no crash
void DoSomething();
};
Foo.cpp
#include ManagedStuff.h
#include Foo.h
// Foo::Foo() { } // AV if not inline.
void Foo::DoSomething()
{
gcroot<ManagedClass^> stuff = gcnew ManagedClass();
.....
}
FooImpl.cpp
#include Foo.h
IFoo* IFoo::Create()
{
IFoo* f = new Foo(); // CRASH if ctor is NOT inline.
f->DoSomething(); //CRASH
return f;
}