To resolve the issue, download and install the following hotfix:
For Sitecore XC 9.1.0: SC Hotfix 377544-1 CommerceEngineInventory 3.0.11
Be aware that the hotfix was built for a specific Sitecore XC version, and must not be installed on other Sitecore XC versions or in combination with other hotfixes. In case any other hotfixes have already been installed on a certain Sitecore XC instance, send a request for a compatibility check to Sitecore Support.
Note that the ZIP file contents need to be extracted to locate installation instructions and related files inside. The hotfixes must be installed on a CM instance and then synced with other instances using standard development practices.