On regulatory sandboxes and actual implementation

Been looking into the concept of regulatory sandboxes, specifically how they're being used in FinTech for various innovations. On paper, the idea of a controlled environment to test new products without immediate, full-scale regulatory burden makes sense for fostering innovation. However, I'm finding it hard to get a clear picture of the actual transition from sandbox approval to full market launch. Are there common pitfalls or significant delays once a concept moves beyond the sandbox? Or is the sandbox approval generally a strong indicator of smoother sailing through full compliance? Interested in hearing any experiences from those who have navigated this.