Got a photo of the torn area?
Sails sometimes tear down that low due to rigging issues, mast bases being too long,
incorrect mast bend.
None of the above would be covered under a warranty.
If you take it to an experienced windsurfing sail repair loft, they will have no problems
taking care of a tear, even in a highly stressed area near a camber inducer.
The luff sleeve.... the luff sleeve from the monofilm.... one of the reinforcements?
Hope this helps,