React Native (with expo) fetch with FormData Network error on Android only

When i try to do a fetch API call in POST with React native (expo SDK 37) using fetch and FormData, everything works perfectly on IOS but it makes a Network error on Android: [TypeError: Network request failed]. I have the same error (network error) if I use axios instead of fetch.

If I replace the formData with empty a {}, it works.I've checked on an emulator and on physical devices (with various Android versions), and i tried to play with headers but no result. And my API has a valide let's encrypt certificate

let url = 'https://my-prod-server/webservice';let formData = new FormData();formData.append('test1','test1');formData.append('test2','test2');let request = await fetch(url, {  headers: {'Accept': 'application/json','Content-Type': 'multipart/form-data',  },  method: 'POST',  body: formData,}).then(response => response.json()).catch(error => console.log('API ERROR: ', error));return request;