EPUB3 Validation Error - Assertion failed: package dcterms:modified meta element mu

[ERROR]content.opf: 3,152: assertion failed: package dcterms:modified meta element must occur exactly once

Getting this on IngramSpark and similar on http://validator.idpf.org and https://www.ebookit.com/tools/bp/Bo/...epub-validator

Line 3 is

<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="uuid_id" version="3.0">
<metadata xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:opf="http://www.idpf.org/2007/opf" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

I do have this in line 10

<dc:date>2019-02-14T00:00:00+00:00</dc:date>

and the below thread indicated to change it to <dcterms:modified> </dcterms:modified> but that doesn't work and returns a load of errors

https://www.mobileread.com/forums/sh...d.php?t=197051

Stuck