Bizarre vertical alignment of multi-line field in Acrobat Pro

Using Acrobat Pro CC (2017.009.20058) for Windows; I'm behind on Acrobat updates due to another issue.

I created a meeting announcement form for my client with the idea that she could open the PDF file in Reader, fill in the details, and print it each month. Three of the fields are multi-line. The one that's two lines long works fine. The four-line and the 10-12 line fields do not. The fields in question are have Rich Text Formatting enabled.

The problem is there's a huge space above the first line of text, and the field won't allow more than two lines to be entered. (No character limit is set.) After much searching, I found a reference to Control-e, where there is a vertical alignment setting. This can't be set in form design mode, but I was able to set it while in Form preview mode. Clicking the top-alignment icon didn't seem to do anything, though. To get the first line of text where it needed to be, I had to set the Spacing Above to -16 for the four-line field and to -68 for the longer field. These settings allowed me to enter all the lines of text I needed.

When I opened the file in Reader to test it, it seemed to work. I put a test paragraph in the field and it seemed to be lined up where I wanted it. This is how it looks when I'm clicked inside the field:

When I clicked outside the field, however, the first four lines of text disappeared. It also prints this way:

Likewise, on the four-line field (in which I'd typed two lines of text), only the second line is visible.

Help?