I agree, the flush is the killer. Fluid drain and refill is my recommendation. That way only a portion of fluid is replaced and not as much gunk is loosened and freed up by the detergents in the new fluid. A flush is more likely to loosen up a bunch of said gunk which in turn starts blocking internals. That's what I've always been taught....

 

PS Every vehicle is different so fair warning if something happens don't cone to my house and throw a wrench at me....

 

my 2cts, i've owned my truck for 20yrs,bgt with 50k,changed tran oil and filter,changed again at 75k,just hit 108k,drained and filled with 1 bottle of CONDITIONER and ran it for couple of hundred miles then drained and refilled with oil and another bottle of conditioner [did not change filter] put thru 123drp and back first sitting then driving it shifting 1-d and down,now just drive normally,works fine,will drive for a couple more thousand miles then drain and change filter using just regular tranny oil maybe even a castrol 75k+ fluid...