hhhmmmmmm!!!!
That's totally annoying.
Poor You!
I've reverse sandwiched, and never had a problem .... yet!
Wonder what happened this time for yours?
Watson, Here's what I do, ....... is there anything different in our techniques?
1st layer flat on table ... taped well with painters tape and/or clamped to edge of the table.
Just a bit of tension on it, but not so much as to distort. KWIM??
Batting, lay on top, and smoothed out flat.
Fold 1/2 over. Spray the fabric and smooth batting in place.
Fold remaining 1/2 over already sprayed area. Spray and smooth.
Final layer ... most times it is the FLIMSY, but the backing if doing things in reverse!
Same process as with the batting, Again, spraying the fabric.
How does this compare?