I had a project where I completely suprised the client and the company within the beginning. It was silky smooth, working on multiplatform ios android,standalone. I wrote the most complex shader I ever made. Everything was great and I even got a bonus for the project.
Then one day. Videos started to stutter. Not playing, completely black on some cases and some devices.
I started to think about reasons. I tried every solution I come up with. No success.
Updated all the codecs, middleware still nothing. Tried to solve the problem for a week. It was a total diaaster and I even thought I a dont deserve to be a developer.

We encoded the videos a few times. Decided to export the original video again, boom! It worked. Theres no particular reason why it worked. But it worked. I guess I am a good developer. Not the best but, eh.