File variable fallback option fails

File variable fallback option fails: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). <!-- 1. If you have a question and not a bug/feature request please ask it at http://forum.serverless.com 2. Please check if an issue already exists so there are no duplicates 3. Check out…