[AW] vertical scrollbar on the right side of the AW is broken

When scrolling vertically in the AW Dopesheet, the scrollbar on the left works fine, but the same scrollbar on the right side is broken (does not slide up and down properly).

repro:
-Open any animation clip that has more animated properties than you can display at once in the AW Dopesheet
or
-Open project, bug scene and select mangagirl
Now use the vertical scrollbar to the left of the AW, it work as expected...
Bug: Use the vertical scrollbar to the right of the AW, does work properly.

see attached gif

this is a regression from 5.2.4f1 (98095704e6fe)
...not repro in this version.

this is repro in 5.3.2p2 & 5.4.0b5 (6a0b0f896e48)