I think it is related to this update from Aug 25th:
* Enhancement – Improved security by running all user-generated content through wp_kses()
by default
It started working after I replaced the line 75 of class-acf-field-message.php from:
echo acf_esc_html( $m );
to
echo $m;
Is there a way to avoid this function from running on the message field?
Thanks!