On macOS, my VertexBuffer is not uploaded when calling QRhiResourceUpdateBatch::uploadStaticBuffer in some configuration.

I am queuing an upload of a static buffer using 

m_resourceUpdate = m_rhi->nextResourceUpdateBatch();
m_resourceUpdate->uploadStaticBuffer(m_vertexBuffer.get(), vertices);

I am using NanoVG which uses an other resourceUpdateBatch and is calling
cb->resourceUpdate(rc->resourceUpdates); (nanovg_rhi.cpp:418) during the call of vg.end(); (main.cpp:166) before my call to cb->beginPass.

In my code, my m_resourceUpdate is enqueued via cb->beginPass(rt, Qt::red, {1,0}, m_resourceUpdate);

If I step in the Qt code, the actual upload happens during setShaderResourceBindings (if it has a uniform buffer) or setVertexInput if I comment out the vg.render() (main.cpp:176)

You need CMake to compile the code

unzip rubug.zip 
cd resourceupdatebatch_bug
mkdir build && cd build
cmake -G Xcode ..

The attached Xcode Metal frame capture shows that the Quad geometry contains 0,0 for the vertices instead of the uploaded one.

However, this works on Windows