After upgrading from v3.6 to v4.0 (v4.1) filters select2 and select2_ajax does not work

Bug report

After upgrading from v3.6 to v4.0 filters select2 and select2_ajax does not work - it only shows empty area after click on it. When click on that empty area, it shows options, but close immediately. This bug is present in v4.0 and v4.1 too.

What I did

filter definition:

$this->crud->addFilter([ // select2 filter
                'name' => 'id_outlay_center',
                'type' => 'select2',
                'label'=> trans('backpack::nou.outlay_center'),
            ], function() {
                return \App\Models\Codelist\OutlayCenterActive::all()->pluck('outlay_center_with_code', 'id_outlay_center')->toArray();
            }, function($value) { // if the filter is active
                $this->crud->addClause('where', 'id_outlay_center', $value);
            });

What I expected to happen

Show options for select2 or line to write characters in select2_ajax filters. ??

What happened

Show only empty area ??

What I’ve already tried to fix it

??

Backpack, Laravel, PHP, DB version

When I run php artisan backpack:version the output is:

PHP VERSION:

PHP 7.2.10 (cli) (built: Sep 13 2018 00:48:27) ( ZTS MSVC15 (Visual C++ 2017) x64 ) Copyright © 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright © 1998-2018 Zend Technologies

LARAVEL VERSION:

v7.10.3@6e927e78aafd578d59c99608e7f0e23a5f7bfc5a

BACKPACK VERSION:

4.1.3@02988a0d14b09e55949781d729060df910f0d94b

[trip-somers]

UPDATE: It occurred to me to look into potential Bootstrap conflicts. I was already using Bootstrap v4 in my app.js which I had set up in my config/base.php to be included on my admin pages. When I commented that out of my config, the select2 filters started working again.

[tabacitu]

Thanks for sharing your solution @trip-somers !