It looks like you had good service the first time around, 245,000 miles with the first rebuild 19,000 miles ago. So if the transmission failed at about 226,000 miles with heavy use there were probably several factors causing the breakage. The main issue may have been loose bearings causing gear tooth mismatch. Then with the rebuild three gears were replaced. Input shaft/gear, counter shaft 5th? not sure what that means, and main shaft 6th gear. Anytime you change one gear, the gear it matches with also needs replaced. If you don't, you get a noisy transmission and gear mismatch which usually breaks teeth again.
Nick