Memory Leak when using QQuickPaintedItem with RHI

Our application uses QQuickPaintedItem to draw custom elements in QML.

eg a decorated line in the attached example.

With Qt 5.15.2 and Qt 6.2.0 beta we detected a rather large memory leak depending on the

used graphics API.

Qt 5.15.2

OpenGL: no leak

Angle_D3D11: no leak
OpenGLRhi: memory leak
Direct3D11Rhi: memory leak

Qt 6.2.0 (current beta)

OpenGL: memory leak

Angle_D3D11: memory leak
OpenGLRhi: memory leak
Direct3D11Rhi: memory leak

On 6.2.0 all backends seem to "eat" memory" even NullRhi.

A minimum example reproducing the issue is found here:
https://github.com/glaure/qt_rhi_qquickpainteditem_leak

The example is just painting "QLineItems" using a repeater.

(It seems to be important to paint more than one item)

The attached memory screenshots use Qt 5.15.2