Graph client for OneDrive upload doesn't work with some accounts

Question

For a few days now, uploads to a previously used OneDrive account have been unsuccessful with an error message:

Status Code: BadRequest, Microsoft.Graph.ServiceException: Code: invalidRequest, Message: Invalid request....ClientRequestId...

However, it works perfectly fine with a newly created OneDrive account. This is where the code gets stuck:

var uploadSession = await graphClient.Me.Drive.Root
    .ItemWithPath(folder + fileName)
    .CreateUploadSession(uploadProps)
    .Request()
    .PostAsync();

I haven't changed anything with the old account. Another user has also encountered the problem with their previously used account. The Azure service associated with the Graph API doesn't report any issues, I'm not aware of any critical updates/version change, and I have no idea where to start from here. In the application, the user connects to their own account and uploads a zip file there.