ClassCastException in tests with temporal filter

Test environment:

ets-wfs20-digiwg 0.3
TEAM Engine 5.0 (as well as 5.1-SNAPSHOT)
beta http://cite.opengeospatial.org/te2/ and local docker environment
WFS: http://cite.deegree.org/deegree-webservices-3.4-RC3/services/wfs200?service=WFS&request=GetCapabilities

Test failure:

Test Name:  with During Filter
Test Description:   DGIWG - Web Feature Service 2.0 Profile, 7.3.3., S.24, Requirement 10; OGC 09-026R2 Temporal Filter CC, A.10
Test Result:    UNTESTED
Reason of Failure: java.lang.RuntimeException: java.lang.ClassCastException: org.apache.xerces.impl.xs.XSElementDecl cannot be cast to java.lang.Comparable

Exception occurs in de.latlon.ets.wfs20.core.wfs20.testsuite.temporalfilter.AbstractTemporalFilterTest#findDateProperties

opengeospatial / ets-wfs20-dgiwg

ClassCastException in tests with temporal filter #6