Eloquent relationship works with seeder, but not with form entry.

I have a many-to-many relationship between Purchase Orders and Shipments.

Shipments are from Vendors through Purchase Orders.

When I use a seeder to set up a few dummy shipments, the eloquent relationship brings up the Vendor's name in the view. If I enter the shipment with a form, it doesn't bring up the name. However, the records exist in the database.

What am I missing?

Tables:

Purchases - has vendor_id 

Shipments - dates and tracking info

Purchase_Shipment - purchase_id and shipment_id

Relationships

Vendor:

    public function purchases()
    {

        return $this->hasMany('App\Models\Purchasing\Purchase');

    }

    public function shipments()
    {
        return $this->hasManyThrough('App\Models\Purchasing\Shipment', 'App\Models\Purchasing\Purchase',
            'purchases.id', 'purchases.vendor_id');
    }

Purchase:

    public function shipments()
    {

        return $this->belongsToMany('App\Models\Purchasing\Shipment', 'purchase_shipment');

    }


    public function vendor()
    {

        return $this->belongsTo('App\Models\Vendor\Vendor');

    }

Shipment:

    public function purchase(){

        return $this->belongsToMany('App\Models\Purchasing\Purchase', 'purchase_shipment');

    }

    public function vendor(){
        return $this->hasOneThrough('App\Models\Vendor\Vendor', 'App\Models\Purchasing\Purchase',
            'purchases.vendor_id', 'purchases.id');
    }

Here are the seeders:

Purchases

        DB::table('purchases')->insert([
            ['number' => 1231, 'vendor_id' => 1, 'status' => 'In Progress', 'active' => 1,
                'date_po_sent' => null, 'date_po_confirmed' => null, 'slug' => '1231', 'all_items_received' => 0],

            ['number' => 1232, 'vendor_id' => 2, 'status' => 'Received', 'active' => 0,
                'date_po_sent' => today()->subDays(6), 'date_po_confirmed' => today(), 'slug' => '1232', 'all_items_received' => 0],

            ['number' => 1233, 'vendor_id' => 3, 'status' => 'Cancelled', 'active' => 1,
                'date_po_sent' => today()->subDays(10), 'date_po_confirmed' => today()->addWeekdays(1), 'slug' => '1233', 'all_items_received' => 0],

            ['number' => 1234, 'vendor_id' => 16, 'status' => 'In Progress', 'active' => 1,
                'date_po_sent' => today()->subDays(6), 'date_po_confirmed' => today()->subDays(5), 'slug' => '1234', 'all_items_received' => 1],

            ['number' => 1235, 'vendor_id' => 50, 'status' => 'In Progress', 'active' => 1,
                'date_po_sent' => today()->subDays(2), 'date_po_confirmed' => today()->subDays(1), 'slug' => '1235',  'all_items_received' => 1],

            ['number' => 1236, 'vendor_id' => 65, 'status' => 'In Progress', 'active' => 1,
                'date_po_sent' => today()->subDays(16), 'date_po_confirmed' => today()->subDays(11), 'slug' => '1236',  'all_items_received' => 0],

            ['number' => 1237, 'vendor_id' => 76, 'status' => 'In Progress', 'active' => 1,
                'date_po_sent' => today()->subDays(1), 'date_po_confirmed' => today()->subDays(1), 'slug' => '1237',  'all_items_received' => 1],
        ]);

Shipments:

        DB::table('shipments')->insert([
            ['id' => 1,'requested_ship_date' => today()->addDays(4), 'expected_delivery_date' => today()->addWeekdays(5),
                'actual_ship_date' => null, 'received_date' => null],
            ['id' => 2,'requested_ship_date' => today()->addDays(22), 'expected_delivery_date' => today()->addWeekdays(26),
                'actual_ship_date' => null, 'received_date' => null],
            ['id' => 3,'requested_ship_date' => today()->addDays(13), 'expected_delivery_date' => today()->addWeekdays(15),
                'actual_ship_date' => null, 'received_date' => null],
        ]);

purchase_shipment:

        DB::table('purchase_shipment')->insert([
            ['purchase_id' => 1, 'shipment_id' => 1],
            ['purchase_id' => 1, 'shipment_id' => 2],
            ['purchase_id' => 2, 'shipment_id' => 3],
        ]);