Because of issues with schema validation (can't properly use doc() in the validate function - see https://github.com/BaseXdb/basex/issues/1324), I'm not using BaseX to do schema validation in my workflow.
But I needed it today to make some result comparisons with my own implementation of XML Validator, and I noticed that using the beta Xerces version which is documented in the wiki http://docs.basex.org/wiki/Validation_Module#XML_Schema_Validation can make it crash, so I thought I should report it here.
Other than that, I noticed one some XML files that it only reports fatal errors, and hides any other non-fatal error. I think it has something to do with the process https://github.com/BaseXdb/basex/blob/86a12cf0c75010b3058c18f81c4689bc511b7c2d/basex-core/src/main/java/org/basex/query/func/validate/ValidateFn.java method but I'm not sure.