Sorry you're having this problem, pre-cuts have been famous for this for a while now. On today's Missouri Star Quilt Company Friday video, Jenny Doan shows how she deals with this problem (at the 1:58 mark). I've been doing it this way for a long time, it works as long as there's not a great big difference in the size.
https://www.youtube.com/watch?v=xXgg...em-uploademail