Users are occasionally experiencing echo on PSTN calls. The E1 ports are MGCP-controlled, and have echo cancel coverage set to 64ms (the default) and have 'echo-cancel erl worst-case 3' configured under each of the voice-ports.
Would increasing the ERL worst case to 6dB have any effect? The other option may be amend the input gain and output attenuation.
The DSPware is 4.4.24, IOS 12.4(13b).