The first sign you set down does not let you type on multiple lines

STEPS TO REPRODUCE:

1. Load a world
2. Set down a sign
3. Type something
4. Press enter
5. Type something else

RESULT:
Everything is on the same line, though the text entry cursor flickers to what should be the correct position.

EXPECTED RESULT:
Text is on multiple lines.

EDIT: It appears the controller was not even part of the issue.