Wikimedia Bugzilla is closed!

It is a custom to escape html tags when referring to the in wikitext with <nowiki> or &lt; unless you actually want to use those tags in wikitext, which doesn't seem to be the case.

I don't see any way how I could fix this in Translate extension itself.

As a workaround I you could try to use the content handler to force them to be text:

$wgHooks['ContentHandlerDefaultModelFor'][] = function( $title, &$model ) {
	if ( $title->getNamespace() == NS_YOURNAMESPACE ) {
		$model = CONTENT_MODEL_TEXT;
	}
	return true;
};