I might miss the target completely here, but you haven’t just switched to using # instead of ## recently?
The usual convention for many people are to use ## for the main titles in any given note, and let the file name be the topmost heading. And if you’re new, which I don’t know if you are (so sorry if I’m mistaken), you could maybe have switched back to using # instead of ##?
See Obsidian Titles/Headers - #7 by robertandrews for a little more information on not using the level 1 headers.
Regards,
Holroy