Thank you for sharing your experience, and we are sorry for the trouble with your 80V self-propelled mower. St. Augustine grass can be dense, and the mower may shut off for protection if it senses too much resistance, especially in taller or wet areas. Regarding the blade, we currently offer only one high-lift option, and without your model number, we cannot confirm compatibility. We also apologize for the unhelpful “undefined” chat response, you deserve better support. Please reach out to our team directly with your mower’s exact model and serial number, along with the battery and charger, so they can guide you through troubleshooting, including cutting height, mowing pattern, and maintenance checks. Our experts can be reached via the online chat (“Chat with an Expert” on the Greenworks Tools page) or by calling 1-888-909-6757. We are here to help get your mower cutting the way it should.