I have encountered a similar issue, as documented here. Notably, dropdowns, tooltips, and select elements do not function in the vo.dev chat environment, although they operate correctly when deployed.
Two days ago, all my Next.js API backend requests initiated from the frontend in the v0.dev chat were appropriately routed through a CORS proxy. Currently, these requests are being made directly from the frontend, which results in failures. The same codebase works perfectly in the deployed environment because the edge functions are returning JSON responses. It appears that there has been a change in how the v0.dev chat environment handles Next.js API calls in the playground.