Welcome to the club ... of mechatronics failures
Symptoms are similar- been driving normally, and a few more aggressive shifts would trigger the transmission error code, and odd/even # of gears would be gone. In my case I lost reverse too.
Either you'd have to swap for a new/used transmission or at least replace the mechatronics.
Some evidence I've found:
Mechatronic Problem
If you read the codes, you may get fault codes related to the valve body also known as the BMW mechatronic. BMW ZF mechatronic are notorious for problems with 2 to 1 st gear downshift or shift flare during the upshift. These harsh upshifts and downshifts are often due to a TTC clutch failure, overheating, damaged solenoid, worn solenoid springs and other problems with the mechatronic unit.
If you checked everything above but are still having problems with your BMW transmission the cause most likely is the mechatronic unit. If you are looking to save money, you can consider replacing only the solenoids in the mechatronics unit/valve body. If you decide to replace the solenoids yourself, remember to change the foam strip that goes between the solenoid terminals and connectors.
https://www.youcanic.com/bmw-transmission-problems/
Indy shop said its the Mechatronic Unit. Which comes to a total of 8k parts and labor haha ooph.
So from my research, it seems best just to replace the whole transmission right? because I've read where people in the same spot as me, replace the Mechatronic, and still the problem persisted.
https://www.m3post.com/forums/showthread.php?t=1957220