Good point there HP, there's nothing worse than subcoat failure....well, except falling over into the wet paint- 'bout the same work to repair.
Been there - done that, used a "cheaper" primer, sealer failed, stopped after the first color coat, resanded * re glazed because the paint ate it, re-primed with quality primer, re-sealed with proper coats of sealer, re-painted. Cost of cheaper primer : 400 bucks & 10 extra days....what a savings.