Hello,
I've tried again with your suggestions, but still encountered the same problem. The dialogues flip through almost instantly, so 3 or 4 lines of text go by in a fraction of a second, without any keyboard or mouse input. Changing the dialogue speed and windowing the game didn't seem to have any effect. Restarting it does seem to alleviate the issue temporarily, so hopefully I can play through the rest in that way.
Best,
Arceus