C++ multiple inheritance with interface

Question

I have a question concerning multiple inheritance. In my project, I want to add support for dll plugins and need an interface for that reason. In the application, I create objects like players and visual objects and hand them to the dll interface. the dll only has the ability to interpret a character pointer as ICharacter for example. My problem occurs, within the application itself:

class IGameObject
{
    virtual const std::string &getName(void) const = 0;
    virtual void setName(const std::string &name) = 0;
};

class IVob : public virtual IGameObject
{
    virtual const Math::Vec3 &getPosition(void) const = 0;
    virtual void setPosition(const Math::Vec3 &pos) = 0;
    // more pure virtual functions
};

class ICharacter : public virtual IVob
{
    // pure virtual functions
};

class GameObject : public virtual IGameObject
{
    GameObject();

    virtual const std::string &getName(void) const override;
    virtual void setName(const std::string &name) override;
    // more virtual function override
};

class Vob : public virtual IVob, public GameObject
{
    Vob(VobType type);

    virtual const Math::Vec3 &getPosition(void) const override;
    virtual void setPosition(const Math::Vec3 &pos) override;
    // more virtual function override
};

class Character : public ICharacter, public Vob
{
    Character();

    // virtual function override
};

Suppose character is of ICharacter

Now, if I want to call character->setPosition(pos); it may crash, since it comes as ICharacter pointer. If I reinterpret_cast<Character*>(character)->setPosition(pos); it, then it may work properly. It seems, as if the vtables got mixed up, but I can't see where that happens. If I reorder the inheritance it may – in some constellation – work.

Process looks like:

Creation (Character*) -> dll interface (reinterpret_cast<ICharacter*>) -> call functions in dll interface, which are 100% part of the original character

If passed back to the application:

dll interface (ICharacter*) -> application (reinterpret_cast<Character *>)

What do I miss?

Thanks in advance

Edit: In fact did I try to dynamic_cast, but that didn't help. Now it crashes in an even earlier call.