I put in some Marvel and let it run 30-45 minutes (couldn’t drive it), changed the oil and filter, and it’s running fine now with no P2646 and no bucking. Drove it for about an hour yesterday with some hard pulls and the issue is gone.
I still would like to know where the oil passage gets its oil from though. The Honda service manual doesn’t get that in depth of telling us where the oil is sourced.