Fail storing uploaded file after Maatwebsite\Excel import in Laravel 5.7

I am using Maatwebsite\Excel import in Laravel 5.7 to process an uploaded XLSX file. After this process, I am trying to store the upload file. However, I'm getting following error:

fopen(): Filename cannot be empty at /Users/myuser/workspace/my-application/vendor/laravel/framework/src/Illuminate/Filesystem/FilesystemAdapter.php:207)

This is my code:

public function import(ImportActivity $request)
{
    $params = [
        'creator_id' => auth()->user()->id,
        'project_id' => $request->project_id,
        'overwrite' => $request->has('overwrite')
    ];

    (new ActivitiesImport($params))->import($request->file('excelFile'));

    $filename = 'activity_import_' . str_random(16) . '.' . $request->file('excelFile')->getClientOriginalExtension();
    $request->file('excelFile')->storeAs('activities', $filename, 'import_files');

    return $this->success();
}

Import is being done properly. If I comment the import part, the store is executed perfectly. The error comes from the store process AFTER importing. I also have tested using static calls for import and store with the same result.

Displaying the content of the uploaded file, I have realized that the uploaded file object changes ($request->file('excelFile')):

Printed BEFORE import

Printed AFTER import

I don't know the cause of that change in the uploaded file object. In addition, it works if I do it in the opposite order, but I only want to store the file when the import process has been carried out properly.

Can someone help me with my problem, please?

Thanks in advance

via Chebli Mohamed