I’m Anatol and responsible for what we call Platform Engineering at SimScale - that is, everything related to the platfom that underlies SimScale: data storage, executing jobs, getting data from and to your browser etc.
We recently replaced a critical part of our system, the long-term storage of customer data, with a new component that will allow us to scale pretty much indefinitely in terms of storage. We tested that component for several weeks on several development systems, but obviously some issues that are now appearing at the scale of our production system were not found by those tests. This is why uploads were failing and currently are again.
Yesterday, we thought we had a workaround for what is happening to uploads, but it seems like that was not enough. We will be working on a proper fix and let you know once we are confident we have found and properly fixed the issue. Until then, we can resolve the issue temporarily whenever it arises, and will do so (I just did that and it works again).