A client's manicure lifted after only two days today. How do I determine if it's the product or the prep work?

A regular client came back for a repair today, saying the gel lifted from the sides after just two days. The product batch hasn't changed. Instead of immediately blaming her for getting them wet, I checked her cuticle condition, the previous prep notes, and the style done that day. I discovered the issue was that the cuticle on one hand wasn't cleaned thoroughly enough, and the top coat capping…