Screen cloning with eglfs_kms does not work on Raspberry Pi 4

When cloning the screen output by setting QT_QPA_EGLFS_KMS_CONFIG the following error occurs when manipulating the screen causing a re-rendering of the scene.

QEGLPlatformContext: eglSwapBuffers failed: 3003
Could not lock GBM surface front buffer!

QT_QPA_EGLFS_KMS_CONFIG:

{
 "device": "/dev/dri/card1",
 "hwcursor": true,
 "outputs": [
 { 
 "name": "HDMI1",
 "mode": "1280x800",
 "mouseDevice": "/dev/input/mouse0"
 },
 { 
 "name": "HDMI2",
 "mode": "1280x800",
 "clones": "HDMI1"
 }
 ]
}