screenlocker turns off the screen after 60 seconds and then turns it back on again

I have two monitors, and I set turn off screen after 60 seconds when screen locked in systemsettings, however I found that when the screenlocker turns off screen, after 10 seconds, it turns on again, and 60 seconds after that, it turns off again...

And when I turned off my second monitor, after the screenlocker turned off the only screen, it would not turn on the only screen anymore.

I thought that might be, when the screenlocker turns off two monitors, the external monitor(with HDMI connected) counts down for 10 seconds and then sleep, after that, KDE detect the external screen is detached, it thought that might be a sign of someone trying to unlock, and then KDE screenlocker turns off both the two monitors.

STEPS TO REPRODUCE
1. set turn off monitor after specific time when screen locks
2. plug in your second monitor and then lock the screen
3. wait for two monitors to turn off

EXPECTED RESULT

the monitors will not be turned on until you tap some key or move the mouse

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Plasma 6.0.3
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.3

ADDITIONAL INFORMATION

openSUSE-tumbleweed, linux 6.8.1, laptop
GPU: Intel alder-lake iris-xe graphics, opensource mesa
two monitors: internal monitor and external HDMI monitor with energe saving functionality