I have done further testing, and it appears that simply enabling a dummy plugin is enough to cause slapd to crash. This plugin code alone is sufficient to cause a crash when syncrepl is enabled:

#include "slapi-plugin.h"

int plugin_init (Slapi_PBlock *pb); int internal_plugin_init (Slapi_PBlock *pb);

__attribute__ ((visibility ("default"))) int plugin_init (Slapi_PBlock *pb) { return 0; }

Therefore, it would seem that there is actually a bug in the openldap code, not in a third-party plugin as originally thought.

What do you need to investigate this bug further?

Thanks!