See https://wordpress.org/support/topic/page-unable-to-reach/

class-amp-base-sanitizer.php.diff

diff --git a/includes/sanitizers/class-amp-base-sanitizer.php b/includes/sanitizers/class-amp-base-sanitizer.php
index 2482db29..e2171079 100644
--- a/includes/sanitizers/class-amp-base-sanitizer.php
+++ b/includes/sanitizers/class-amp-base-sanitizer.php
@@ -486,8 +486,12 @@ abstract class AMP_Base_Sanitizer {
 		}
 		$should_remove = $this->should_sanitize_validation_error( $validation_error, compact( 'node' ) );
 		if ( $should_remove ) {
-			$element->removeAttributeNode( $node );
-			$this->clean_up_after_attribute_removal( $element, $node, $validation_error );
+			try {
+				$element->removeAttributeNode( $node );
+				$this->clean_up_after_attribute_removal( $element, $node, $validation_error );
+			} catch ( Exception $e ) {
+				error_log( sprintf( 'Failed to remove attribute %s from element %s', $node->nodeName, $element->nodeName ) );
+			}
 		}
 		return $should_remove;
 	}