BG 3&4 problems

Angeldcf

Our BG Elementals work extremely well, but we have leaks in the back with our BG 3.0s & 4.0s.  I saw that a major difference was the Elementals had the PUL across the interior back.  The OS 3&4s have the cotton up to the seam (hence the leaking when he naps).  They've been washed tons of times.  I've tried folding the back over/inside, but it doesn't stay.  Any tips?