After digging in the source code, I confirm the tags are correctly removed from the ability system component when the ability ends.
The problem lies in the output of the owned tags I display each tick.
I also tried with the built-in GetDebugStringFromGameplayTagContainer, but with the same outcome.
![2017-05-10 11_19_38-RWC [DebugGame] - Unreal Editor.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/a/0/1/a01257f7fcc21ba2c7d110e6a56c6ecdfa379965.png)