I appreciate you taking the time to answer me! I closed Joplin from the window then the system tray. Nothing was fixed. So I rebooted the whole computer, and it didn't fix anything.
personalizedrefriger (above) was the person who mentioned "render", and I guess I wasn't sure what he meant either, but I tried his solution, and it didn't help.
These below are lines that got corrupted. I had Joplin open and looked at that data and saw it was corrupted. I can't imagine what caused it. They are some financial notes I need to get back. With my steps above, they still didn't reappear. Additionally, I want to be able to trust Joplin that this won't happen ever again. Here are the lines. What do you think?
KaTeX parse error: Expected 'EOF', got '#' at position 40: …) CONFIRMATION #̲:
KaTeX parse error: Expected 'EOF', got '#' at position 40: …) CONFIRMATION #̲:
KaTeX parse error: Expected 'EOF', got '#' at position 40: …) CONFIRMATION #̲:
KaTeX parse error: Expected 'EOF', got '#' at position 40: …) CONFIRMATION #̲:<span style="c…
katex parse error: Expected 'EOF', got '#' at position 40: …) CONFIRMATION #̲:<span style=;" color:="" 25323d="">
Thank you for your help!