I’m no tech but I’ll try to get you started until one of our resident techs answers.
To my knowledge, tranny coolant lines from the rad are steel and not hose.
If the coolant and the tranny fluid are mixing, there may be a leak internally in the rad between the rad and the rad/tranny fluid cooling tank.
As far as I know the only fix is to replace the rad as I doubt there is any aftermarket ‘weld’ in a can that would repair this.