[Freeswitch-users] mod_expr random not thread safe?

I'm building a test for voice quality, and I need to randomize the silence preamble. At the same time, other sessions are recorded into a tmpfs file. <action application="set" data="rand_val=${expr(randomize(&x);ceil(random(0,100,&x)))}"/> I noticed that when I added this, the audio recordings started to have gaps of dropped audio 40ms long. Are the randomize() and random() thread-safe at all? It seems like the whole FreeSWITCH process freezes when one of those functions gets executed.