stuck in onProgress while concatenating two wma files

I am joinin two Windows Media Audio (wmav2) files that have exactly the same properties.

String[] command = {"-i", "concat:storage/emulated/0/soundrecorder/temp.wma|storage/emulated/0/soundrecorder/temp2.wma", "-c", "copy", "storage/emulated/0/realencodedfileconcat.wma"};
ffmpeg.execute(command, new ExecuteBinaryResponseHandler() {

    @Override
    public void onStart() {
        Log.d("FFmpeg", "concat onStart()");
        }

    @Override
    public void onProgress(String message) {
        Log.d("FFmpeg", "concat onProgress(): " + message);
    }

    @Override
    public void onFailure(String message) {
        Log.d("FFmpeg", "concat onFailure(): " + message);
    }

    @Override
    public void onSuccess(String message) {
        Log.d("FFmpeg", "concat onSuccess(): " + message);
    }

    @Override
    public void onFinish() {
        Log.d("FFmpeg", "concat onFinish()");
    }
    });
} catch (FFmpegCommandAlreadyRunningException e) {
    // Handle if FFmpeg is already running
    Log.d("FFmpeg","FFmpegCommandAlreadyRunningException: "+e.getMessage());
}

But the FFMPEG gets stuck in onProgress()

08-04 14:59:06.772 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onStart()
08-04 14:59:06.798 28543-28650/com.audiorecorder.wel.voicerecorder D/FFmpeg: Running publishing updates method
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress(): ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   built with gcc 4.8 (GCC)
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libavutil      55. 17.103 / 55. 17.103
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libavcodec     57. 24.102 / 57. 24.102
08-04 14:59:07.415 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libavformat    57. 25.100 / 57. 25.100
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libavdevice    57.  0.101 / 57.  0.101
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libavfilter     6. 31.100 /  6. 31.100
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libswscale      4.  0.100 /  4.  0.100
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libswresample   2.  0.101 /  2.  0.101
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   libpostproc    54.  0.100 / 54.  0.100
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress(): [asf @ 0xb54a5000] Estimating duration from bitrate, this may be inaccurate
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress(): Guessed Channel Layout for  Input Stream #0.0 : mono
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress(): Input #0, asf, from 'concat:storage/emulated/0/soundrecorder/temp.wma|storage/emulated/0/soundrecorder/temp2.wma':
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   Metadata:
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():     encoder         : Lavf57.25.100
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():   Duration: 00:00:07.63, start: 0.000000, bitrate: 128 kb/s
08-04 14:59:07.416 28543-28543/com.audiorecorder.wel.voicerecorder D/FFmpeg: concat onProgress():     Stream #0:0: Audio: wmav2 (a[1][0][0] / 0x0161), 16000 Hz, 1 channels, fltp, 128 kb/s

Why? How to remove this error and complete the concatenation?

cropsly / ffmpeg-android-java

stuck in onProgress while concatenating two wma files #222