Unwanted recordings in the root of spool folder

I’m using FreePBX
I wanted my recordings to occupy less space, so I changed setting “Call Recording Format” (in Settings - Advanced settings) to “WAV” instead of default “wav”. It makes FreePBX to store recordings in small gsm format instead of huge PCM.
Everything was great, recordings became very small (about 10x). But I noticed that all my recordings were in the root of /var/spool/asterisk/monitor, all in one folder. In other words, I have folders tree with small recordings (/var/spool/asterisk/monitor////recording.wav) AND all those recordings, but in PCM format, all in the /var/spool/asterisk/monitor). So, I have two copies of every recording on HDD: gsm one and pcm one.
If I delete PCM files from root of /var/spool/asterisk/monitor, nothing bad happens, CDR monitoring works. I think these files are not deleted by FreePBX in the process of conversion. Is there a way to get rid of them?