The fix is to NOT use GM branded ATF. Use 100% Synthetic atf such as Mobil 1 or AMSOIL. The oem fluid does not hold up in these transmissions, especially the 8sp because of lower viscosity requirements. GM engineers may set standards but the bean counters control who gets the bid to supply lubes and all they have to do is meet the MINIMUM spec, no more, no less. End result, transmission failures, afm lifer failures etc.
GM does not care what happens once the warranty expires, its your problem then. Their dealer will gladly take your money to repair them.