As an exshop mechanic and ex pro downhill team mechanic, I’ve never, in 20 years, torqued a cassette to what it say’s too, it’s about having a sense of what is tight and what is rite,by the sounds you’ve gone too far…, Take off the cassette and check for scoring on the bearing retainers, perhaps the treads on the locknut are too deep for Dt Swiss hubs? Microspline is a new standard, you’ve got to accept these issues