The answer isn't jumping out at me. But thinking out loud:

- Seems like lack of lube on the drum to support surface (no kidding)
- I see nothing wrong with your mods to help prevent this! But I have not done those mods myself.
- Although I don't like a big 1/8" dia hole for oiling the sprag rollers, that is an old mod so it shouldn't be the primary cause.
- If something else is bleeding lube or restricting lube flow, the combo with the 1/8" hole might be starving it. Since the shaft to support gets the fluid before the drum, it might be OK when the drum isn't getting enough.
-The fluid passage mods for the governor removal need more scruntiny. But you seem to have taken care of it.