Fired my apprentice today after he botched a CertainTeed shingle install on a steep pitch

Up here in zone 5 Pennsylvania, winters hit hard and you can't afford screw-ups on a roof like this. I had this 20-year-old kid I'd been training for three months, and today on a tear-off and re-shingle job with CertainTeed Landmark shingles, he straight-up nailed the starter strip wrong and caused a bunch of wind-lift issues before we even got halfway. Cost me an extra two hours fixing his mess, and the homeowner's already bitching about the delay, so I cut him loose right there on site, told him to grab his tools and go. Seen this same kinda thing posted in the Roofing Pros Facebook group last week, guys saying apprentices just don't listen anymore. Frustrated as hell, been doing this 15 years and it's like starting over every time. Now I'm short-handed for a slate repair job next week, and materials alone on that one's pushing $4500. Anyone got tips on finding reliable help without burning through more cash?

man that sucks, had a similar deal with my helper mangling a GAF ridge vent last month, felt like i was babysitting the whole time.