See the attached screenshots. The markup seems correct, but somehow the ) is gone in Summit.

Original markup:

::: spoiler Bonus panel
![Bonus panel](https://midwest.social/api/v3/image_proxy?url=https%3A%2F%2Fdiscuss.online%2Fpictrs%2Fimage%2Fb2f22051-739c-463f-88b7-6aa3e6406785.png)
:::

Edit: Actually, re-checking my post, I can see even in the code block that the bracket is gone, please use a browser to check the actual source.