I've my panel Test.LockedGrid that extends Ext.grid.Panel, initializing the store and some predefined and locked columns using an overridden initComponent method. It works normally.
If I try to extend my panel defining Test.LockedGrid2 I get some errors. I think that the problem is caused by the Ext.grid.locking.Lockable mixin that calls the initComponent of Test.LockedGrid twice (for normal and locked subgrids) repeating also the store and columns configuration from Test.LockedGrid.
This is the fiddle with unlocked columns: i
f you try to lock columns setting
lockButtonColumn = true
on ?Test.LockedGrid, the fiddle doesn't work.

Is my Test.LockedGrid and Test.LockedGrid2 design wrong ? I miss some special configuration in extended class to get it work correctly ?