We found a bug in the latest version of Kendo related to the reordering columns in Treelist when inside a Grid DetailTemplate
See the Dojo below to replicate the problem:
Expand the detail row under a grid row and attempt to drag one of the treelist column titles to the left or right and note that an error is thrown.
Uncaught TypeError: Cannot read properties of undefined (reading 'lockable')
Let us know when you have a workaround for this as it prevents us from promoting this version of Kendo to our production environment.