Created attachment 146436 [details]
Video demonstration.

In the Discover update page, when I click on an update item ("system update") to see the sub-items, the scroll bar is broken. That is to say, that it works only at a certain place of the bar. 

STEPS TO REPRODUCE
1: Open Discover and go to the update page.
2: Click on "system update" to display all the packages that will be updated.
3: Click on the scroll bar on the right and use it fully.

OBSERVED RESULT
If there are a lot of items, the scroll bar is broken in some places, it is not constant.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon
KDE Plasma Version: 5.23.5
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.3