Titles are not translatable

I’m not sure what the issue is here, but I have successfully used this plugin with WPML multiple times and have had no issue translating the content of the titles.

It looks like, I am not the only one having this issue:
https://wpml.org/forums/topic/problem-with-accordion-blocks-phil-buchanan/

I’m not sure if the problem is your plugin or WPML, but maybe you can do something from your end to fix this.

Based on the link you provided, it looks to be an issue with WPML and they have a fix for it.