In a very specific situation where multiple versions of OpenBuildings Designer are used on a project it is possible for an existing Structural.rul file content to be deleted.
We have identified a bug in Update 4 and subsequent versions where a check for read-only status was missing for the structural rules file.
In the context of system testing or trouble shooting this results in an open DGN as read-only operation carried out by an administrator privileged user with an OpenBuildings Designer newer than the operational version updating the structural rules file with a new version number and also rewriting the active content.
The next time a file is opened with the operational (earlier) version the application is unable to read the updated file (our dataset content is not backwards compatible) and the rules are not available to users.
The next time is opened by an administrator privileged user with the operational (earlier) version the file content is lost during the rewrite.
This has now been fixed and will be available in OpenBuildings Designer Update 9 early in Q1 2022.
This scenario can be avoided by always using the correct version of OpenBuildings Designer with operational systems.