Data entered into a form is garbled

I created a form and set all the fields' font size as auto. The file was saved as a "Reader Extended PDF" with "Enable More Tools" selected.

In all my tests, the data is entered corrected, right size, fits in the box. But the data entered by my first user of the form came back messed up (K    A    R    E    N      W    A   T   K), overflowing the field. No matter what I do I cannot replicate how the user's data ended up so wonky.

Btw, the signature field was set with an action to make the file read-only, so that the data could not be changed afterward. Because the file is now read-only, I cannot export the data. I was hoping that I would find the overflowing data if I exported the data, but I cannot. (This actually leads to another question I will post later.)

Any ideas as to why the data would all end up like this?