Observing a schematron issue with utc timing occuring only with DVB 2018 xsd

[kjerbi]

When using an mpd validation with dvb 2018 xsd I have a warning about the absence of utc timing (mpd1). When I add the utc timing (mpd2), I get a schematron issue.
Is it a potentially a validation issue or something wrong with the way I insert the utc timing?
Many thanks

Khaled

mpd1:

mpd2: