Looks like we can't reproduce the issue or there's a problem in the test case provided.
[4.1RC]A scroll bar does not move by a lock column.
It is a question about gridPanel.
Horizontal scrolling is displayed on gridPanel.
Two or more "lock" columns of gridPanel are carried out.
When the width of the column which lock(ed) is expanded to the maximum, it becomes impossible to move scrollbar.
Is this phenomenon a bug?
That's a phenomenon of a locked grid in which you have expanded the locked (non horizontally scrollable) region to fill all the width you allocated for it.
You've fill your width with non scrollable stuff! So no scrollbars.