Downloaded a fresh copy of the v0.12 today.
Could it be that once this error is triggered, it somehow is corrupting all dialogues? Maybe it is disabling all dialogues?
Sorry if I am meddling, but as a developer myself, I'd suggest to look for alternatives to any text based keys, if possible. I have no experience with or any idea about construct, but I am quite sure there must be a way. I recently developed a dialogue system for my new project as well, so I understand that it can be a bit challenging and time consuming, but it will be worth it, saving you from a lot of possible headache.