Pg Upgrade failing as it is not able to start and stop server properly

Hi,

While upgrading the PostgreSQL database from 9.1.4 to 9.6.4 version on
windows 2012 server, Pg_upgrade is failing as postgre service start and
stop are failing because of time outs. I got the information as using -m
immediate mode with solve the problem, but we are interested to know the
root cause of this issue.
Without -m immediate, the server start and stop commands will simply wait,
till command timeouts and they fail.
There is no load on the server that could cause a performance issue.

Below is the failure snippet from pg_upgrade_internal.log file.

Checking for presence of required libraries ok
Checking database user is the install user executing:
SELECT rolsuper, oid FROM pg_catalog.pg_roles WHERE rolname = current_user
AND rolname !~ '^pg_'
executing: SELECT COUNT(*) FROM pg_catalog.pg_roles WHERE rolname !~ '^pg_'
ok
Checking for prepared transactions executing:
SELECT * FROM pg_catalog.pg_prepared_xacts
ok

If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.

Performing Upgrade
------------------
Analyzing all rows in the new cluster
"c:\EMC\AppSync\jboss\datastore_96\engine\bin/vacuumdb" --port 50432
--username ^"apollosuperuser^" --all --analyze --verbose >>
"pg_upgrade_utility.log" 2>&1
ok
Freezing all rows on the new cluster
"c:\EMC\AppSync\jboss\datastore_96\engine\bin/vacuumdb" --port 50432
--username ^"apollosuperuser^" --all --freeze --verbose >>
"pg_upgrade_utility.log" 2>&1

*failure*
"c:\EMC\AppSync\jboss\datastore_96\engine\bin/pg_ctl" -w -D
"c:\EMC\AppSync\jboss\datastore_96\data" -o "" -m fast stop >>
"pg_upgrade_utility.log" 2>&1

Below are the pg_upgrade logs pertaining to the failure. Please suggest any
solutions to fix this issue.

Regards,
Kiran G