Deadlock after some calls

[aduiliosilva@xxxxxxxxxxxxxxxx (Aduílio)]

I'm using pjsua 2.2.1 built for Android.

In my app I have an activity starts a Service that runs in background to 
allow the app to receive the events. The Service instantiates a class 
(PJsipManager) that makes interface between my app and pjsua2 (loads 
libpjsua2.so lib, instantiates the Endpoint and calls libCreate(), 
libStart() and libInit(), etc). The Service listens all events and take 
actions accordingly. After some calls the app stops with the following 
deadlock:

----- pid 26895 at 2014-06-16 16:06:53 -----

JNI: CheckJNI is off; workarounds are off; pins=0; globals=347 (plus 5 
weak)

DALVIK THREADS:
(mutexes: tll=0 tsl=0 tscl=0 ghl=0)

"main" prio=5 tid=1 NATIVE
   | group="main" sCount=1 dsCount=0 obj=0x4164ce40 self=0x4156e500
   | sysTid=26895 nice=0 sched=0/0 cgrp=apps handle=1073955156
   | state=S schedstat=( 0 0 0 ) utm=77 stm=20 core=0
   #00  pc 00021ad4  /system/lib/libc.so (__futex_syscall3+8)
   #01  pc 0000e8e0  /system/lib/libc.so
   #02  pc 002723e8 
/data/app-lib/com.softphone.android.beta-2/libpjsua2.so (pj_mutex_lock+100)
   at org.pjsip.pjsua2.pjsua2JNI.Account_getInfo(Native Method)
   at org.pjsip.pjsua2.Account.getInfo(Account.java:92)
   at com.softphone.android.service.JService.makeCall(JService.java:507)
   at 
com.softphone.android.activity.JMainActivity$1.onReceive(JMainActivity.java:227) 

   at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:759)
   at android.os.Handler.handleCallback(Handler.java:733)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:136)
   at android.app.ActivityThread.main(ActivityThread.java:5086)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:515)
   at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 

   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
   at dalvik.system.NativeStart.main(Native Method)

What might cause this?
I already tried:
- set max threads to 0 and main thread only, but doesn't even register;
- set max threads to a higher number like 6, but app stops even faster.