Spurious system error events and log file warning entries claiming invalid Regex patterns are created whenever Regex policy condition matchers are initialized. These events and log entries occur regardless of the origin or the correctness of the Regex pattern.
Release : 15.8
In DLP 15.8 there was some refactoring of the Regex code which resulted this regression.
Fixed in DLP 15.8 MP1 check Issue ID DLP-38889 in 15.8 MP1 release notes.