shared cell update

This has always been a bl**dy frustrating nuisance, however I am now finding inconsistencies across users in how this is handled. 

Normally in order to update a shared cell from library, I would use Replace cell extended, with options replace and global selected. select the new definition from library and select the cell to replace. 

However, this does not always work, sometimes the cell will just not update/replace. Now I am finding that whilst I can update shared cells in a file, other users cannot, despite following the exact same workflow and process. 

It may or may not be something to do with the below. When I select an updated cell definition, the Update cell definition button activates, allowing me to easily select the cell and update. However, for other users this does not activate????? 

Help tells me that this is supposed to be for updating parametric cell definitions, but for some reason it works for me on normal shared cells.