On knotty backs i've had linen pop off when drawn. Currently, I tightly wrap inner bicycle tube around the limb, heat that to reliquify the hide glue, rub the limb with my hands to draw out excess glue, and let it cool. The next day I remove the tube and let it dry. This works fine for me.
Another thing with linen (raw flax): it's so strong (very high modulus of elasticity) that a small difference in placement (especially on knotty crowned backs) can make a big difference. Wheigh the amount to put on each limb carefully.