hi
I couldn't help but endorse the prep stage. All clients are not the same, I used to have the same problem long ago, but I realized that some clients need extra prep time to really keep from lifting. Make sure and get the rid of cuticle on the side walls too.
To get repeat service, let your customer know that you are working on improving the technique for their particular situation. Find out where the lifting starts (side walls, eponichium), and review what could have gone wrong, so communicate with them and show your concern. People like to know that you are interested in them.
I guarantee that your customers will be coming back for that service and there will be no more lifting providing you prep well. I hope this post is not too late.