Recurring cracking in transmission housing?

I owned my truck listed above for a year before the transmission cracked right above the pan and before the extension housing. Dropped the pan and extension housing months previously to replace the park rod. Replaced the transmission and 2 months later it cracked in the same spot as previously. I decided to weld the crack, and it worked for about 5 months, but it will no longer hold any fluid, I believe it blew a gasket or cracked again but I’m not certain of which. What would cause the crack to return twice and is it worth replacing the transmission again?