Answer
When an address locator stored on a network location is accessed by a map document in ArcMap or a project in ArcGIS Pro, a lock is created on the address locator that prevents other map documents or projects from rebuilding, renaming or modifying the address locator. This is problematic if the address locator is stored on a network location such as a shared folder that is accessed by multiple users. There is no way to view if an address locator is locked, and any attempt to rebuild the locked address locator fails.
This is common with Python scripts that are automated to rebuild an address locator on a regular basis, causing ERROR 000005.
This article details the best practices in deploying address locators on a network location in an organization. The following are ways to allow for multiple users to use the address locator while avoiding locking issues.
Share address locators as geocode services
Once an address locator is created, the locator can be shared as a geocode service to an ArcGIS Server. As a geocode service, the service can be accessed by many users simultaneously through different applications in the ArcGIS platform, including ArcGIS Desktop, ArcGIS Pro, ArcGIS Online, or Portal for ArcGIS. The geocode service can also be used in web applications. For more information on sharing an address locator as a geocode service, see ArcMap: About sharing your address locator as a geocode service.
Share address locators as locator packages
A locator package is an address locator or a composite address locator along with its participating locators packaged into one portable file for sharing in an organization, or via ArcGIS Online. By storing a locator package (.gcpk) on the network location, the locator package can be pulled from the network location and unpacked into an individual machine that creates a local copy of the address locator (stored in C:\Users\<user profile>\Documents\ArcGIS\Packages). This avoids any locking issues with the address locators on the network location and improves performance, since the locator is accessed from the local machine and not across a network.
To rebuild or update the locator package, the copy stored on the local machine can be shared as an updated version of the locator package to the network location, or stored as an archive of the address locators. For more information on locator packages, see ArcMap: About sharing an address locator as a locator package.
Share address locators as mobile map packages
A mobile map package consolidates maps into a single file (.mmpk) that can be shared with an ArcGIS organizational account or copied directly to a mobile device. Address locators can be deployed with mobile map packages (.mmpk) through ArcGIS mobile applications like Navigator for ArcGIS and Explorer for ArcGIS, and applications developed using ArcGIS Runtime SDK 100 and later. For more information on mobile map packages, see ArcGIS Pro: Mobile map package.
Note:
The above recommendations are for user-created address locators. For StreetMap Premium for ArcGIS locators, a license must be obtained, or else this is a violation of the terms of service.