One of our projects migrated their file-repository to another one during a major release.

Instead of giving this task to an experienced programmer, they gave it to the head of the respective dev department due to the usual release panic.

Soo.... He wrote the migration tool. It was executed during the release. Everything seemed fine so far.

A few days later. Someone from the above project came to my team due to some "strange behaviour on the production database".
They reported that they couldn't download some of the user's documents due to unknown reasons.

After quickly analyzing the current state of the new file-repository, we concluded that the affected documents did not exist in the new repository.

Then we took a look at the so called migration tool...
Well.. After nearly 30 min. we knew the root cause for that.
They only migrated the first 4 levels of the folder structure. Due to the assumption that "we don't use deeper nesting". (Facepalm)

As the head of their department wrote it, no one seems to questioned it either. Nor did they made a code review and ended up with a tool with hard coded urls to the production db, no version control, no build tool, no ci, nothing. Breaking nearly every possible company standard.

However.. That's not it. When analyzing their migration tool we noticed another even more dangerous thing.
They mixed up the id generation of the migrated documents resulting in a random assignment between customers and documents. Which is quite bad as this contains sensitive information. E.g. passports

They offered us quite a nice amount of money to fix this until EOB. We declinded as it was simply not possible in that time, but agreed to support them with the new tool.

After some time I heard that they migrated production again. And they fucked it up again. They never talked to us after we offered them support...

The third and final migration was written by us. Not only migrated it correctly. It was also way faster. By factor 20.

In the end we haven't gained anything from this rushed project as the penalties were piling up due to this fucked up migration.
After all this time I'm not sure who is to blame. In my opinion, partly all of them.
Head of department who can't and shouldn't code.
Seniors who didn't review the code and didn't ask for help.
Release mgmt who put way too much pressure on the devs.