Q: Transmission not operating correctly.

I have used YourMechanic before, but don't think this can be done, in my drive way. Van stopped moving, while driving. On side of road, found passenger side wheel was not engaged. When spinning wheel, it felt like axle splines were not quite seated. With very limited tools, I banged and pushed to ensure axle was seated. While it did not seem to move, it did engage. Van drove with no symptoms, until it happened again, after few hundred miles. Then knowing I was wrong, I pulled axle, hoping to see splines gone or chewed, indicating it was not fully seated. Axle was perfect. In all the movement and jostling, something re-engaged. Van made it almost around the block. I was/am convinced problem is inside transmission and was hoping it would move long enough to get to a shop. Now for the question: is there any chance it is not internal transmission problem (sensor, control etc.) and YourMechanic can repair? If not, can you recommend shop for Kia transmission repair/rebuild
My car has an automatic transmission.