Anyone here have up-close-and-personal experience with the inside of Miata transmissions? Specifically an ND would be great, but I'll take any insight. I'm trying to understand how the input shaft bearing is lubricated. I thought it would be lubricated by the transmission oil, but then I watched this video (of a 5 speed, so not an ND but still a Miata):

https://youtu.be/u8rTYlK8Q0g?t=126 [Embed]

Picrelated is a couple frames from the video. In the top frame, it's showing the front of the input shaft bearing which has the ball bearings exposed. The second frame shows the back of the input shaft bearing, and you can see it doesn't seem to be open to the rest of the transmission. Can anyone explain? Does the input shaft bearing have its own sealed lubricant?

Just took my 2020 ND on a road trip, taking the odometer from 14.9k to 18k in the course of 6 days, and while it held up great, towards the end of the trip, I noticed basically every symptom of early input shaft bearing wear, which is not an ordinary mode of failure AFAIK, not to mention it's a 2020 which is supposedly one of the years without systemic transmission issues, so I'm trying to figure out what could have gone wrong.