[Bug] Cannot set property name of which has only getter. Where does it come from?

[VRa3]

Current behavior:

I wrote a function that allows me to upload files by request when needed (e.g. creating default project without UI clicking). Here's code for it :

cy.wait(1000)
    .window()
    .then((win) => {
        const requestObject = {
            method: 'POST',
            url: `${(win as any).remote_service_base_url}/my-endpoint`,
            headers: {
                authorization: 'bearer ' + (win as any).abp.auth.getToken(),
                'content-type': 'multipart/form-data',
            },
        };

        cy.fixture(FilesPage.singleFile, 'binary')
            .then((file) => Cypress.Blob.binaryStringToBlob(file))
            .then((blob) => {
                const formData = new FormData();
                formData.append('projectId', projectId);
                formData.append('comment', '');
                formData.append(FilesPage.firstFileName, blob, FilesPage.firstFileName);

                cy.request({ ...requestObject, body: formData }).then((response) => {
                    expect(response.status).to.eq(200);
                    cy.wait(500);

                    if (amountOfFiles === 2) {
                        cy.fixture(`${FilesPage.filesPath}/${FilesPage.secondFileName}`, 'binary')
                            .then((file) => Cypress.Blob.binaryStringToBlob(file))
                            .then((blob) => {
                                const formData = new FormData();
                                formData.append('projectId', projectId);
                                formData.append('comment', '');
                                formData.append(FilesPage.secondFileName, blob, FilesPage.secondFileName);

                                cy.request({ ...requestObject, body: formData }).then((response) => {
                                    expect(response.status).to.eq(200);
                                    cy.wait(5000);
                                });
                            });
                    }
                });
            });
    });

And this works just fine, it does its job.

However, in next test suite I use cypress-file-upload package and method attachFile

cy.log('before attachFile');
cy.get('p-fileupload input[type="file"]').wait(1000).attachFile({
    filePath: filePath,
    encoding: 'base64',
});
cy.log('after attachFile');

to upload files using the UI and I get this error. You can see that after using attachFile method the following cy.log is not invoked:

The stack trace for this error is here, I couldn't find hints there:

What I could notice, is that if I skip the function that uploads files by request the attachFile method works as expected.

Desired behavior:

A desired behavior here would be working functionality of attachFile method no matter if upload by request is used or not.

Versions

cypress: 8.3.0
cypress-file-upload: 5.0.8
operating system: windows 10 20H2
browser: Chrome 96

I've seen topic about this error message on stackoverflow, and tried solution, but this doesn't solve the problem.