Sorry, I can't say I tested it very extensively in NVL mode. I'll try to make a note to look into it more later. I have some guesses as to what the issue might be. I know Renpy likes to reset the whole textbox in ADV mode whenever it updates, so maybe it does something similar in NVL mode. If true, then the time being given to the displayables would be reset and not a lot I could do about that outside of awkwardly storing timers in globals in a way that'd be really messy. Though given your description, it that might not be the case and could be something else. I'll try to look into it when I have time but been busy lately.