Created attachment 130966 [details]
demonstrating the inconsistency by scrolling up by just one step and down by just one step repeatedly.

SUMMARY


STEPS TO REPRODUCE
1. Open Kdenlive
2. Make Audio Mixer Visible
3. Hover over the scrollbox underneath the audio slider and scroll up and down

OBSERVED RESULT
The value is increased and decreased in inconsistent increments, scrolling up once does not increase the value by the same amount as scrolling down would decrease the value.

EXPECTED RESULT
Scrolling up one step would increase the value by the same amount as scrolling down one step would decrease it.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.70.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION
1) In the attached video, I've demonstrated the inconsistency by scrolling up by just one step and down by just one step repeatedly. 
2)Scrolling on the slider itself works fine and is consistent, but the value increments are inconsistent (scrolling down once: -0.50, twice: -1.27, thrice: -2.08) when it should probably follow an increments like -0.50, -1, -1.50 etc.