I created a Slide Library for a customer, which he really liked. He was playing around on my Dev-System and also on my Test-System. Everything went better than expected so we decided to jump over and release his library for his colleagues. But unfortunatly it didn't go that well on the production system. He was working a couple of days with it and got always problems with uploading some presentation.
When I was back in the office I had to take a look into it, so I started testing with the Dev-System and of course our Test-System. But to my dissappointment it worked fine, so the problem was only somewhere in the production system.
Next thing I checked was the event log, but also nothing unusual. Some typical errors, but nothing new or in any way related to my slide library. Than I read through the SharePoint Logs while uploading a file, just in case it throws an exception or an error of any kind. But also nothing there.
So what else could it be? I took a look at the last installed patches on the systems, but also: nothing related to PowerPoint or the slide libraries.
Finally I gave up and took a look at the PPTX-files I got. Everything looked fine, but when I was running the "Inspect Document" command under "File / Info / Check for Issues" it throws an error, telling me something about "Picture crop information". It was indeed possible, that this information brought up an random error while uploading this file. I clicked the "Remove All" button, but no matter how often I clicked that button and saved the file, it always came up with the same error.
My last attempt was to save the PPTX-file a little bit old school. I decided to save the file als PPT and check out if the error still pops up while uploading. To my surprise it worked fine and I got no error, but I'm still not sure why it came up. I will keep investigating, maybe I will find a proper solution, but for now saving in PPT makes the most sense.