I cannot speak for Intel. But it is not very likely that there's a bug of their GPUs or an "engine problem" that appears nowhere except in your shader.
I almost don't dare to mention it, but can it be possible that the problem is your shader and not the Intel GPU? For instance, when you're using a shader mode that your graphics hardware does not support, it will render your model without shader. This has nothing to do with Intel GPUs, it's just a missing fallback technique in your shader - that's what I'd look for at first.
