In general, the error means that you are trying to call a proc or a query that is nowhere defined. When that happens, Osiris assumed you want to defined a database with that name, but it refuses to allow you to do so if the name does not start with DB_ (exactly to prevent you from mistyping names and then not getting any error).
In this particular case, it's because I made an error in the description of DB_CheckPoint: the guards don't automatically start a dialog, but instead PROC_CheckPointDialogue(_Player, _Guard) is called. See the updated https://docs.larian.game/Osiris/Shared/DB_CheckPoint
for more information.
Since there is no definition of PROC_CheckPointDialogue in your mod, you get the error above. Implement it as described on the updated wiki page, and it should (finally) work fine.