Qt3D: 4 Frame Delay when using BufferCapture

When using the BufferCapture component to read/write data to a SSBO, there is always a 4 frame delay between the rendering, and receiving the "dataChanged" signal from the QBuffer.

I understand a small delay is needed to get the data back, but this seems to be stuck on exactly 4 frames which is strange. I have tried increasing/decreasing the framerate and changing the buffer size,  and I still seem to get the answer precisely on the 4th frame.

Is this normal behavior ? Is there something I can do to get the data quicker ?

I have attached a small example that counts frames before the answer. Click the window to get it working, results are displayed in the console.

First click is slow (framegraph init I imagine). For all the following tries, it takes exactly 4 frames to get the answer. You can change the framerate in main.cpp.

Thank you.