Hi @victoria Im late to the party here. But I just had the same issue with a file upload to our custom API. Your workaround {{ {...importFile.files[0], "data": importFile.value[0] } }} fixes this. Since this is now a standing issue for some time: it seems this is not officially documented anywhere [1][2]. This sent me on a 2 hour bug hunt. It would be nice if behaviour like this could be documented outside of support forums.
[1] Perform REST API requests | Retool Docs
[2] File Input | Retool Component Library