Sporadic complete audio failure affecting entire department - RTP routing issue on 3CX Cloud instance

[Dre1902]

Environment:

• 3CX Version: 20.0 Update 10
• Hosting: Hetzner
• SIP Trunk: Deutsche Telekom CompanyFlex
• Clients: 3CXPhone for Windows (latest Version)
• Affected users: All users in "Innendienst" department

Problem Description:
All users in our Innendienst department experience sporadic but complete audio failure during calls. When the issue occurs, neither party can hear anything. The problem affects the entire call from the moment it is established and does not recover mid-call. After hanging up, the next call may work normally.


Key findings:

• Problem occurs on both internal and external calls
• Affects all users in the department regardless of headset or PC hardware (tested 3 different headsets, multiple PCs)
• 3CX audio quality log shows RoundTripTime of 2,315,878ms on affected calls
• Quality reports show 0 packets received from the trunk side on affected calls, while the client side sends normally
• Call mode is always Transcoding (PCMA on trunk side vs OPUS on client side)
• Wireshark capture confirms network traffic is clean - packets flow normally between local network and 3CX Cloud, no packet loss on network level
• "PBX delivers audio" is enabled for affected users but does not resolve the issue

What has been ruled out:

• Hardware (3 different headsets, multiple PCs tested)
• Network/Jitter (clean according to 3CX logs and Wireshark)
• Audio device selection (all other audio devices disabled)
• Codecs (multiple combinations tested)
• Local network routing (Wireshark confirms clean traffic to/from 49.12.191.59)
• SIP Trunk (issue occurs on internal calls too)
• Firewall/QoS (configured and verified on WatchGuard M290 and Aruba 2930F)

Suspected cause:
RTP routing or transcoding issue within the 3CX Cloud instance itself. The problem appears to be internal to the PBX as network-level traffic is confirmed clean.


Request:
Please analyze server-side logs for affected calls, specifically RTP stream routing and transcoding processes for Innendienst department users.

 

[NikosT_3CX]

@Dre1902 as I can see your PBX is not hosted by 3CX, its self managed so we do not have access to your machine.
I would recommed telling your 3CX Partner to open a ticket to our Support Portal and then we can take it from there.

 

[Alphabetic]

Check your server hardware and if there is a backup scheduled to run.

Id be more suspicious of the VPS than the installation.

 

[Claas Felix Beyersdorf]

Does this happen to members of other groups also?
Does this happen for all members at the same time (one is having the problem do others have problems at the same time?

Do you have some Edge Protection on the clients that might cause problems?