Calls drop in the middle of the conversation randomaly

Hi

I have this weird problem on ZAP channels, channels are disconnected without a reason. here is my zapata.conf:

[channels]
;hardware channels
musiconhold=default
answeronpolarityswitch=no
hanguponpolarityswitch=yes
busydetect=yes
busycount=8

;default
hidecallerid=no
callwaiting=no
callprogress = yes
threewaycalling=yes
transfer=no
rxgain=8
txgain=0
echocancel=yes
echocancelwhenbridged=yes
echotraining=yes

has anyone had this problem before? this does not happen for all the calls, its happens randomly without any pattern…any idea?

Thank you all

post cli output when it happens? maybe a zap debug?