I export a rule project from Decision Center (A) as a zip file and re-import this rule project zip into another instance of Decision Center (B). I found that the rule artifacts are missing even though the rule project is created.
This is likely due to the difference of the persistence locale defined in the two Decision Center instances.
Resolving the problem
Before importing the rule project into Decision Center (B), make sure that its persistence locale is the same as the one defined in Decision Center (A).
You can check and define the persistence locale in the Decision Center Enterprise console: sign in as an administrator (rtsAdministrator by default), navigate to Configure > Administration > Installation Settings Wizard > Step 4: Set Persistence Locale. The documentation about the Installation Setting Wizard can be found here.
* Note that the persistence locale can only be changed when there is no rule project persisted in the database.