It helps if you have access to a pressure tester. You don’t mention doing a pressure test. Testers can be purchased or can be made; even from a bicycle pump.
The gearcase would be drained of oil….the tester hooked up and build pressure to 6-8 pounds. Submerse the gearcase and see where the bubbles are coming from.
A member here did some instructional videos a few years ago on gearcase re-seals. Even though you may know the factory procedures….some of his methods are proven where others not so much. Have a look; I always learn from his videos.
https://youtu.be/MABn9YR4Gw8?si=py8V0j_l1urOyZE-
