He doesn't always make statements of truth, he sometimes does and sometimes destroys things that make an incorrect statement.
A thinking machine called 'truth-a-tron', designed to only make true statements, answer questions correctly and destroy anything that makes an incorrect statement, had succeeded in performing these functions before it made the following statement and blew itself up: "I always make statements of truth".
The designers of 'truth-a-tron' have no idea why it identified its last words as being false. Assuming that 'truth-a-tron' didn't malfunction, do you?
(I'm sorry in advance for the difficulty that will almost definitely be had for anyone attempting to explain this).