We tried to repro the issue by setting up below sample.
https://github.com/OfficeDev/Microsoft-Teams-Samples/tree/main/samples/bot-file-upload
However, for us file is being uploaded and downloaded successfully and we can access the file in 'Downloads' section.
Thanks,
Prasad Das
*************************************************************************
If the response is helpful, please click "Accept Answer" and upvote it. You can share your feedback via Microsoft Teams Developer Feedback link. Click here to escalate.