borderlayout splitter jump while dragging

Steps to Reproduce

https://zkfiddle.org/sample/28g5vvt/1-borderlayout-splitter

if the browser width is not big enough, the bug won't reproduce.
drag the splitter in the borderlayout.

Current Result

the splitter jump to another position and the west part shrink

Expected Result

drag like normal splitter and the size of west should not shrink

Debug Information

Workaround