Enable in the config dialog in Editing > Text Navigation: [x] Allow scrolling past the end of the document. Further, disable dynamic word wrap.

Scroll past the end of the document. As soon as you navigate in the last line, the view jumps by scrolling up.

Research on this: The trace is:
KateViewInternal::updateCursor > makeVisible() > viewLineOffset() in:
  else if ( c > viewLineOffset(startPos(), linesDisplayed() - m_minLinesVisible - 1) )

Say you have 5 lines, i.e. 0...4, and c is in (4, 5), the viewLineOffset always returns (4, 0) when dynamic word wrap is disabled. This basically is the error that needs to be fixed.