I think the Grid locked column(s) must be have a maximum width for resizing (Grid.width - VerticalScrollBar.width).
Because when you want to resize locked column more than grid width then you cant see other columns after resizing. Now, if you click on resized column then grid auto scroll to resized width and cannot comeback.
And now, if you double click in resizable vertical column line then this column auto resized and all column disappear from grid.
What happens when you have a locked column(s) is you have two grids in an hbox layout basically. So you only have the total width to view the grids of the parent panel. So if the parent grid panel has a width of 400 and the left inner grid has a width of 400, then you have 0 for the right inner grid.
When the locked columns can be resized with mouse, i do resize column width to out of grid then i expect to resize again to default size with mouse, but i cant comeback to first size. and must be i do refresh browser, and this is not good solution.