Https://serverfault.com/questions/129491/asterisk-dropping-calls-with-an-ast-yyerror

can anybody go on this url and tell me…this waring can make any exception due to which server will come out from asterisk -r and calls would get stop.

because these warning come usually on my server since last 3 years hence i dont think this will cause any issue…

In other words, cause Asterisk to crash. The only things that cause Asterisk to crash are bugs in Asterisk, bugs in third party code linked with it, and resource starvation problems.

For general guidance on what to do when Asterisk crashes, see https://wiki.asterisk.org/wiki/display/AST/Getting+a+Backtrace However note that some crashes result in a semi-controlled shutdown, in which case you need to find the error report at the start of the crash, which will not be the parser error you mention, and breakpoint the code that generates that. My guess is that you have a fully uncontrolled stop.

The 8 year old thread adequately describes why you would get the warning, but only in the circumstances that applied to the OP for that thread. It is certainly not something that would be even likely to cause a crash.