Clearing timestamp when changing date field to empty value

Just noticed that the timestamp value remains saved when deleting the value of a datetime field (did not try it with a date field). However, the display string is removed from storage.
As a result, if I try to filter the timestamp after removing the datetime value, it still applies the old timestamp value.
Here is my code:

add_filter( 'rwmb_meta_boxes', 'twt_register_meta_boxes' );
function twt_register_meta_boxes( $meta_boxes ) {
    $meta_boxes[] = array(
        'id'         => 'specials-c',
        'title'      => 'Specials',
        'post_types' => 'page',
        'context'    => 'normal',
        'priority'   => 'high',
        'revision' => true,
        'include' => array(
            'ID' => array(14),
        ),
        'fields' => array(
            array(
                'name'   => '',
                'id'     => 'specials',
                'type'   => 'group',
                'clone'  => true,
                'sort_clone' => true,
                'collapsible' => true,
                'default_state' => 'collapsed',
                'group_title' => '{title} {date_display}',
                'fields' => array(
                    array(
                        'name' => 'Featured Image',
                        'id'   => 'img',
                        'type' => 'single_image',
                        'image_size' => 'medium'
                    ),
                    array(
                        'name' => 'Make Headline Image Clickable',
                        'desc' => 'to open up larger',
                        'id'   => 'img_clickable',
                        'type' => 'checkbox',
                        'image_size' => 'medium'
                    ),
                    array(
                        'name' => 'Date Display',
                        'desc' => 'e.g. September 6-13, 2019',
                        'id'   => 'date_display',
                        'type' => 'text',
                    ),
                    array(
                        'name' => 'Time Display',
                        'desc' => 'e.g. Noon-5pm',
                        'id'   => 'time_display',
                        'type' => 'text',
                    ),
                    array(
                        'name' => 'Title',
                        'id'   => 'title',
                        'type' => 'textarea',
                        'rows' => 2,
                    ),
                    array(
                        'name' => 'Content',
                        'id'   => 'content',
                        'type' => 'wysiwyg',
                        'options' => array(
                            'textarea_rows' => 6,
                            'teeny'         => false,
                        ),
                    ),
                    array(
                        'name' => '(Optional) Start Display At',
                        'desc' => 'Keep empty to start displaying right away',
                        'id'   => 'display_start',
                        'type' => 'datetime',
                        'js_options' => array(
                            'stepMinute'      => 15,
                            'showTimepicker'  => true,
                            'controlType'     => 'select',
                            'showButtonPanel' => false,
                            'oneLine'         => true,
                        ),
                        'inline'     => true,
                        'timestamp'  => true,
                    ),
                    array(
                        'name' => '(Optional) End Display At',
                        'desc' => 'Keep empty to have the website not automatically hide it',
                        'id'   => 'display_end',
                        'type' => 'datetime',
                        'js_options' => array(
                            'stepMinute'      => 15,
                            'showTimepicker'  => true,
                            'controlType'     => 'select',
                            'showButtonPanel' => false,
                            'oneLine'         => true,
                        ),
                        'inline'     => true,
                        'timestamp'  => true,
                    ),
                    array(
                        'name' => 'Inactive',
                        'id'   => 'inactive',
                        'type' => 'checkbox',
                        'desc'  => 'to preview inactive specials add ?preview to the URL'
                    ),
                ),
            ),
        )
    );
    return $meta_boxes;
}

add_shortcode('twt_specials', 'twt_specials_shortcode');
function twt_specials_shortcode() {
    ob_start();
    $specials = get_post_meta(get_the_ID(), 'specials', true);
    ?>
    <div class="twt-specials-listings">
        <?php
        foreach($specials as $special) {
            if(!empty($special['inactive']) && !isset($_GET['preview'])) {
                continue;
            }
        $local_timestamp = current_time( 'timestamp' );
        if ( ! empty( $special['display_start']['timestamp'] ) && $special['display_start']['timestamp'] > $local_timestamp ) {
            continue;
        }
        if ( ! empty( $special['display_end']['timestamp'] ) && $special['display_end']['timestamp'] < $local_timestamp ) {
            continue;
        }
            ?>
            <div class="twt-special-listing-c">
            <div class="twt-special-listing chalkboard-bg content has-black-background-color">
                <?php if(!empty($special['img'])) {
                    if(!empty($special['img_clickable'])) {
                        $url = wp_get_attachment_url($special['img']);
                        echo '<a href="'.$url.'">';
                    }
                    echo wp_get_attachment_image($special['img'], 'medium_large', false, array('class' => 'special-img'));
                    if(!empty($special['img_clickable'])) {
                        echo '</a>';
                    }
                }
                if(!empty($special['date_display']) || !empty($special['time_display'])) {
                    ?>
                    <div class="special-meta row justify-content-center extra-padding">
                        <?php if(!empty($special['date_display'])) { ?>
                            <div class="col-auto"><i class="icon-cal" aria-hidden="true"></i><span class="screen-reader-text
">Date</span> <?= $special['date_display']; ?></div>
                        <?php } ?>
                        <?php if(!empty($special['date_display'])) { ?>
                            <div class="col-auto"><i class="icon-clock" aria-hidden="true"></i><span class="screen-reader-text
">Time</span> <?= $special['time_display']; ?></div>
                        <?php } ?>
                    </div>
                    <?php
                }
                if(!empty($special['title'])) { ?>
                    <h2><?= nl2br(apply_filters('the_title', $special['title'])); ?></h2>
                <?php }
                if(!empty($special['content'])) {
                ?>
                <div class="content">
                    <?= apply_filters('the_content', $special['content']); ?>
                </div>
                <?php } ?>
            </div>
            </div>
            <?php
        }
        ?>
    </div>
    <?php
    $specials_output = ob_get_clean();
    if(!empty($specials_output)) {
        return '<div class="specials-output">'.$specials_output.'</div>';
    } else {
        $twt_options = get_option('twt-global-content');
        return '<p style="text-align:center">Sorry, there are no specials posted right now. Please check back later or <a href="'.($twt_options['fb'] ?? '').'" target="_blank">follow us on Facebook</a>.</p>';
    }
}

Can you check into it and fix it if applicable? Thank you!