Observations:
- issue may not happen on the 1st repair, but usually happens on succeeding repairs
- /extractlzma process shows, in Process Monitor, a repeating SHARING VIOLATION error when extracting the .msi file
- in Process Explorer, the Process Handles lower pane of the parent process, msiexec.exe, reveals that the .msi file is opened
- killing the /extractlzma process, makes the repair resume to completion