Threads stripped out sounds like wear and tear, not defect.
Did you wire wheel the heck out of them and apply lubricant before adjusting? - self induced.
Did you have adequate thread engagement? - self induced.
Did you torque the jam nut and use locktite to hold it fast and prevent wallowing? -self induced.
I would imagine cracked welds would be the only thing they would warranty long term based on the typical use of a lift kit on a jeep. I don't know the details of the RC warranty, but if it isn't a "what ever happens, even if it's from abuse" warranty you're probably stuck. Cost for adjustable arms is not the worst, or move up to a bomb proof warranty type vendor with a reputation for better parts. That's gonna be much more than 95 bucks.
Pro-rated your arms only cost you 19 bucks a year for the use you got out of them. I'll bet you won't wear the next ones out before the body turns to powder.
I'm back on my court mandated Rx. Other than the drool shorting out my keyboard, I'm here to help!