reduce(resize) the width of Task Name will occurs problem

When we reduce the width of Task Name column, width of other columns(E.g. months column) is not there is blank space in gantt.
When we increase the width of Task Name column it will work perfactly and horizontal scroll bar comes for gantt but in reducing case we have face issue.

can you please clarify how to reproduce the issue?
For example on this demo -
Everything seems working ok on initial setup, but probably you have some additional settings?