Did you install core components only, as I mentioned?
Here's the error:
[StopService] OpenService() failed for service 'BHDrvx86' with error ERROR_SERVICE_DOES_NOT_EXIST while creating rollback action.
2016-05-24T10:59:02.360Z WARN I SIS [StopService] Returning true for create rollback action.
2016-05-24T10:59:02.360Z WARN I SIS [StopService] OpenService() failed for service 'BHDrvx86' with error ERROR_SERVICE_DOES_NOT_EXIST.
2016-05-24T10:59:02.360Z WARN I SIS [StopService] Returning ACTION_COMPLETED_SUCCESSFULLY.
2016-05-24T10:59:02.360Z WARN I SIS [DeleteServiceInternal] OpenService() failed for service 'BHDrvx86' with error ERROR_SERVICE_DOES_NOT_EXIST.
2016-05-24T10:59:02.360Z WARN I SIS [DeleteServiceInternal] Returning ACTION_COMPLETED_SUCCESSFULLY.
Try this solution:
SEP 12.1 installation rollback because bash driver failed to start.
1. Run Cleanwipe if old instances of SEP are present on the system.
2. Copy an unmanaged client setup to the machine. (The SEP or SEPx64 folder from Fileconnect, not exported from the manager.)
3. Install Symantec Endpoint Protection 12.1 with only core components.
a) Run setup.exe from the Unmanaged installation files.
b) Choose Custom settings
c) Install only core components (Make sure Virus, Spyware and Basic download, PTP and NTP are not selected).
4. If installation of core components is successful, proceed to step 5. Do not restart the system
5. Start the setup again and install only Virus and Spyware Protection (No sub components should be selected.)
6. Reboot the machine
7. Post reboot, verify if bash drivers are working properly. Run the following query in a command prompt
a) for a 32-bit machine run "sc query bhdrvx86"
b) for a 64-bit machine run "sc query bhdrvx64"
Win32 Exit code usually is 0x0. For a failed start the Exit code is 0x57. If the exit code is still 0x57 reboot the machine again and check for the status.
8. Install rest of the features (i.e. NTP and PTP).