Mixmonitor beeps stops once you have more than 20 calls

Hi there, we are having an issue, since we provide the option to record calls, we need to announce a beep to allow callee and caller o know they are being recorded. it seems to work with only one call, but as soon as more calls come in to the system the beeps will stop until load goes to 3 calls then it starts to play beeps again.

has anyone experience this, we can see spychan sending the beep to the group of calls but no beeps are heard.please advise.

our dialplan
exten => trunk-+123456789,1,MixMonitor(/opt/${EXTEN}.wav,B(8)p)
exten => trunk-+1123456789,n,Dial(PJSIP/+1912345678-1260508@trunk-out,wTt)
exten => trunk-+1123456789,n,Hangup()

again thank you for any help on this matter.

I forgot to tell that our version of asterisk which is Asterisk certified/13.18-cert2 built

still feels like a bug, we had to define LIMIT_PLAYAUDIO_CALLER and LIMIT_PLAYAUDIO_CALLEE both to yes in order for it to work, so far it is working, whcih is not the proper behavior, now when load stars it wount stop playing.