Warning: Skipping the old school core oven method bit us hard last week

Last week at the shop, we tried to cut corners and skipped the core oven. My grandpa used to swear by baking cores slow and steady. Now we've got this quick-set stuff that's supposed to be a game changer. But it totally failed when we poured, and cores just disintegrated. Tbh, I miss the reliability of the old ways. Anyone else deal with this? Maybe we should go back to basics sometimes. Your thoughts?