Error: "Warning, Guide name could not be blank" when saving > 115 Sections

Everything was working fine, but now I cannot save the Guide (Page Order).

I have 116 Sections.
I can add a new Section.
I can reposition the new section in the hierarchy.

But, when I press Save to Save the new position, the page refreshes as normal but the new position is not saved.

Instead, the plugin displays the error:
“Warning: Guide name could not be blank”

TESTS
The guide name is not blank.
I have checked all the section data, and all have all three required values.
I see no errors in the browser console.

If I DELETE a few sections from the end of the list, then SAVE the list, the bug disappears.
If I add new sections to the list, the bug reappears at the same point: 115 records.

The database appears to be correct:

DATABASE
documentor table

doc_id	post_id
1	2997

documentor sections table

sec_id	doc_id	post_id	type	upvote	downvote	slug
1	1	2998	0	0	0	start
2	1	3002	0	0	0	requesting-membership
3	1	3003	0	0	0	configure-your-profile
4	1	3004	0	0	0	logging-in-and-out
5	1	3005	0	0	0	configure-a-user-account
6	1	3006	0	0	0	new-user-notifications
7	1	3007	0	0	0	approving-a-new-user
8	1	3008	0	0	0	oversings-requirements
9	1	3025	0	0	0	the-user-interface
10	1	3026	0	0	0	search-and-advanced-search

…

106	1	3261	0	0	0	the-outline-tree-view
107	1	3262	0	0	0	the-board-view
108	1	3263	0	0	0	the-column-view-single-stack
109	1	3264	0	0	0	the-timeline-gantt-view
110	1	3265	0	0	0	task-panel-views
111	1	3266	0	0	0	the-pad-view
114	1	3273	0	0	0	for-protocols-medicaldental
115	1	3274	0	0	0	working-together
116	1	3275	0	0	0	driving-your-organization-sprints

ERROR OCCURS HERE: guide.php

//save all sections of guide
		public static function save_sections() {
			check_ajax_referer( 'documentor-sections-nonce', 'sections_nonce' );
			global $table_prefix, $wpdb;
			$sorders = ( isset( $_POST['reorders-output'] ) ) ? sanitize_text_field($_POST['reorders-output']) : '';
			$docid = ( isset( $_POST['docid'] ) ) ? intval($_POST['docid']) : '';
			$docpostid= ( isset( $_POST['doc_postid'] ) ) ? intval($_POST['doc_postid']) : '0';
			$sectionsarr = ( isset( $_POST['sectionObj'] ) ) ? $_POST['sectionObj'] : '';
			$doc_title = ( isset( $_POST['guidename'] ) ) ? sanitize_text_field($_POST['guidename']) : '';
			if( empty( $doc_title ) ) {
				_e("Warning: Guide name could not be blank","documentorlite");

https://wordpress.org/plugins/documentor-lite/