Multiple uploads from different users and different folders

I have an upload API using Multer that works fine so far, but when 2 or more users upload at the same time in their specific folders the files are exchanged in the folders, and sometimes the files go only to one of the folders. I need my API to save the file in the folder the client requested.
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The issue provides an attached code image but names no repository file or test. Start by reviewing the upload API's Multer configuration and reproduce simultaneous uploads from different users and folders. Done means each uploaded file consistently reaches the folder requested by its client.

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