Asterisk is playing wrong voice file in IVR


My company recently has launched a IVR project with telco using the Asterisk. We’re using SS7 signaling points. Our IVR service is runnig from two servers at the same time. Same configurations are there in both servers, just OPC/DPC is different. Each server has installed 3 E1 cards - one is TE820 octal-span and other 2 is TE435 quad-span (Digium card) in each server.

Telco gives us the CIC range and point code for each server. CIC range is same for both server but only point code is different. Please note that, at the same time we can handle around 900 calls as we got total 30 E1 connection from telco end. Currently most of the time of the day, calls are around 450+ in both servers and it increase till 700+ calls at the same time in peak hours (15:00 - 00:00).

Now lets come the point, what issues we are facing to handle these much calls. Actually the problem is when we are getting more than 100+ calls at the same time, users are experiencing with voice play. They are listening wrong voice, sometimes voice is playing from the middle of the voice and sometimes at the end of the voice once call is getting connected to our IVR servers. Note that all are incoming call (IBD). But as per CLI console log, we’re not getting any abnormality for dialplan (extensions.conf). This is the major problem which we are currently facing.

Also note that, after midnight in off-peak hours (03:00 to 06:00) there are very less call below 50. That time there is no issue at all in the IVR system. Everything is running as expected. No voice playing issue, no auto DTMF issue. Opps!! I forget to tell you one thing that, sometimes we are facing DTMF issue. DTMF is pressing automatically. Customer’s complaining that they didn’t press any DTMF, but as per CLI log we can see the DTMF. Even I’ve tried by myself there is really an DTMF issue, which is automatically pressed (for sometimes not for all the time).

IVR service is currently running in production server. This is really very risky to do much experiment as I’m not expert in Asterisk.

Software versions are as follows:
Asterisk 13.16.0
DAHDI Version: 2.11.1

Can you please suggest me how I can recover from this problem? If you need anymore information please let me know.
Thanks in advance.