The error message we see in Designer is "Tables could not be updated: one or more unresolvable database divergences". The core-service.log shows a myriad of errors regarding colum updates with NULL values in non-nullable columns. The objects and fields come from objects that were not touched in the update.
I made the following observation: when I create a project from a snapshot, then change the field to have the desired alias, then deploy, I get the above mentioned error message; however, the extraction rule is now active. Now when I create a new project from a snapshot and deploy, there is no error.
During the whole process I am not making any database changes, just adding the alias.
To me, this looks like a Designer bug.