If I enable the highlight colour button in the format toolbar, the mouse cursor will scroll the viewable page, a brief jump, by crossing the toolbar/document regions border.

I believe nothing should happen to the document without a selection in play; the document shouldn't scroll by hover alone, only if I'm including a selection like a mouse button down/drag while pushing the viewable area, or a type of shift-select or discontiguous-select. 

The amount of scroll jump seems unpredictable, but I suspect it is dependent on the time span of a critical moment. If rulers are turned off, it seems to jump farther. The scroll jump is always upwards. I had trouble narrowing down the minimum content required to trigger the effect, but maybe a third of a page, in view unrelated. The cursor's original position within the document doesn't seem related; after border crossing the scroll jumps from the current view. Effect can be repeated; I can scroll an entire document to the top by waving the bucket cursor back and forth over the toolbar/document border. 

To reproduce in Writer:
- create document and content to span at least one page
- scroll down enough so some content is hidden above the viewable area
- select highlight colour button in toolbar; the tool state not the pull down
- move mouse cursor document across the toolbar/document border, will scroll view then change to bucket
- return mouse cursor to toolbar across the toolbar/document border, will scroll view then change to pointer
- rinse and repeat until document top is reached

Workaround: 
Doesn't scroll if I avoid the toolbar/document border. Can accomplish this by dragging the mouse cursor outside the toolbar region across the window border, then back into the document content region across a window side border. Because a workaround is odd but easy, I decided to label this minor. Hard to break the habit though.