I have seen similar lagging in the settings page on a couple of occasions and never been able to pinpoint what is going on . For me, running in python native, when it happens, it seems to be tied to the virtual environment of whatever branch/pycharm project I am running. When it happens, if I start from a different project, or from an exe build, it is perfectly fine.
Seems like it might be a deep PyQT issue more than a logic issue.