This looks like a memory leak:

        screenResource = vc_dispmanx_resource_create(VC_IMAGE_ARGB8888, screenInfo.xres, screenInfo.yres, &imagePtr);

screenResource is not disposed of directly. Maybe this disposes of it indirectly:

        vc_dispmanx_display_close(display);

If not, we need to find a way to explicitly dispose of screenResource.

Not a critical bug because screen capture is only used by tests and is not available to applications.