Can't upload theme to Portal

Hey community,

since yesterday, I seem to be unable to upload themes the SAP Cloud Platform Portal Theme Manager. I add the zip file, click on save and enter my credentials. But then it starts to hang. The login window and the busy indicator never go away:

There are no useful logs in the console.

When I look at the network requests, it always fails after the fourth one that accesses a directory with the theme name as you can see here:

It sure isn't a problem with the themes (I used them before) and probably also not with my portal site (I tried multiple ones on different sub accounts).

Any suggestions as to what could be the problem?

Best Regards,

Patrick