ios - NSXMLParser crash in xmlFindCharEncodingHandler -

an ios app has been parsing same xml feed last year , half has developed intermittent crash inside [nsxmlparser parse]. crash logs indicate instantiate nsdata object url , use [nsxmlparser initwithdata:] create parser. snippet of stack trace follows:

0   libxml2.2.dylib                 0x366eb1fc xmlfindcharencodinghandler + 124 1   libxml2.2.dylib                 0x366f0f84 xmlparseencodingdecl + 416 2   libxml2.2.dylib                 0x366f2ed8 xmlparsexmldecl + 304 3   libxml2.2.dylib                 0x366fb688 xmlparsechunk + 808 4   foundation                      0x32753d5e -[nsxmlparser parse] + 198 

the crash reported is

exception type:  exc_bad_access (sigbus) exception codes: kern_protection_failure @ 0x00000000 

i should note performing parse , download in background inside nsoperation's main method.

has ever encountered such crash, , if have tips on how resolve? have reached out maintainers of xml feeds ask if there issues character encoding, indicate no changes have been made.