Carbon and other friction particles from the friction bands would leak out into the oil, polluting it, and therefore ZF, in a technical notice, suggested at least one adjustment when the issue was discovered. The oil in the torque converter must be changed at least twice to guarantee a proper renewal percentage since it is not always possible to drain it directly (no drain plug). Maybe they figured out the fundamental issue and fixed it in newer gearboxes. Changing the oil and filter won't hurt anything, except maybe your money, as long as you use the right stuff.