Random G.729 copy protection errors

In the last two weeks I had three instances where on a “module reload” command I got the error “Failed to initialize G.729 copy protection!” when the G.729 codec was loaded, resulting in the need to restart Asterisk completely. After the restart, everything works normal again. The license files are in the proper place (/var/lib/asterisk/licenses), have the right permissions, “astvarlibdir” points to the right dir. No other files than the license files are in /var/lib/asterisk. What else could cause this strange, random error?