Warranty issue for sure. Sounds like a simple fix. But watch to see what they do to fix it. The engine should stall before the clutch gives at those hours.
As others have said;something not right. I have the same model but in HST, however my L2250 was gear and never did anything similar to what you described. My "go to gear" when brush hogging the pastures was always hi-first. Dealer should square you away on this.