Hard Disk Activity widget shows constant writing to disk

I’m using the latest Plasma5 installed with Kubuntu 22.04 LTS and I’m mostly satisfied.

I have only one question regarding the Hard Disk Activity widget installed in the taskbar: when clicking on the small graph icon, it constantly shows a 12 or a 16 MiB writing speed with, while according to System Monitor and htop (and the PC disk activity lamp) there are no ongoing writing processes.

Any help, please?