detail file locking

Hi, Using freeradius 3.0.25 on centos 7 I have a configuration with a "detail" module writing to a file with locking = yes I have a type = detail listener on that same file. Under some load, apparantly, very sporadically a packet seems to gets lost. Am I correct to say that with locking = yes , there should never be any packet lost due to the reader renaming the file while the writer is writing to it ? How would be a good approach to further troubleshoot this ? -- Regards, Thor