Asterisk Crashed

I got this error while trying to conference a call between three parties.

[Oct 7 12:53:12] ERROR[24121] bridge_softmix.c: Failed to acknowledge timer in softmix bridge.

What could be a reason and what could i do to resolve it ?

Although you have indicated an error (which you didn’t note in the subject), you have provided no evidence of a crash.

This appears to represent an internal logic error in Asterisk, and the only way to avoid it is probably to not use the soft mix function.

You should gather all the required debugging logs and submit a bug report, but don’t expect a fast resolution.

However, first check you are not using an out of date version, as the bug may already be fixed, and if you try to report against an old version, you will just be asked to upgrade before going any further.