direct2d RenderTarget cause Qt Ui crashed

[psxc233]

I create a Qt program with 64 widgets, I used direct2d to play video on every widget and used map<HWND, CComPtr<ID2D1HwndRenderTarget>> to save renderTarget. But when the number of renderTarget over 30, the qt program doesn't have any response while the video can play correctly while the program window can move/maximum/minimum. The same thing can work well on MFC.