On regulatory sandboxes and actual implementation challenges

Been reading up on regulatory sandboxes, seems like a brilliant way to foster innovation without over-regulating too soon. But I'm struggling to find much detail on what happens after a project exits the sandbox. Is it a smooth transition to full compliance, or do teams often hit major roadblocks then? My concern is that the sandbox environment might not fully prepare a project for the full weight of existing frameworks, especially for something novel like a DeFi protocol. Any thoughts on real-world experiences here, particularly around how the compliance burden scales post-sandbox?