After a legacy system is re-engineered, it is important to perform compatibility testing so as to identify the differences and reduce the introduced bugs. We can first apply symbolic execution to obtain an exhaustive set of test cases, then use them to check the compatibility of the old system and the new one. However there may be a lot of failed test cases which are a mix of erroneous and allowable incompatibilities. To locate the causes of failures detected during the testing, we apply multiple statistical bug localization techniques. We are able to localize 90% of the incompatibilities in 10% of the code for an industrial application with around 20k lines by Tarantula. And we identify the characteristics of failure causes which are difficult to be detected by statistical bug localization.