file not found error on file upload on openlightspeed server on VPS (only)

I have Javascript code for uploading a file, see codesandbox. The code works on localhost and on a codesandbox-server but not on a VPS at Hostinger, with OpenLightSpeed and Nodejs preinstalled. I CAN upload file to Hostinger VPS uploads folder if I use SSH to connect to the VPS and then run 'node index' (which opens a port on localhost:3000).
On the Codesandbox server the file is uploaded correctly, on the VPS I get 404 file not found error. Payload data however show correct filename in both cases, see:


I assume it is related to a setting on the OpenLightSpeed serversoftware or to a VPS setting at the webhosting provider's server but don't know where to start looking. Any ideas?
The webpage shows up fine, the issue is what happens when clicking the uploads button.
1. initial page:

2. after choosing file:

3. after clicking upload button:


And looking into the payload, it shows that the filename was actually processed correctly, only not uploaded:


Is that an issue that relates to the listener setup? What exactly would be wrong with that setup?