This works only if we have one fieldset appearing.
If you duplicate the fieldsets and test it again, you will notice that, if we have two fieldsets, the links that trigger should also change, but they don't, making the link text to be absurd.
Am I using the wrong tool for this job, or is it a logic issue on this code ? Or both ?
What are you wanting to happen with multiple fieldsets when the add translation button is clicked. Do you want a translation line to be added for each fieldset, or just for the last one?