Need Help: Weird Issue with Timestamps & the Datepicker

Hello. I’ve run into an odd problem and have run out of ideas as to why this is occurring. I was hoping maybe someone has had this issue before and can point me in the right direction so I can clear this bug up.

I’m on cmb v2.9, the site is running on PHP 7.2.34 with WordPress 5.8.1, and I have tried disabling plugins, changing PHP versions, and all of the troubleshooting basics.

So, what’s actually happening. I’m using a metabox with a type => text_date_timestamp. When I use the datepicker to choose a date, it stores the date in the database with the correct timestamp(1630454400). When you view the post on the front-end, the date shows up correctly(September 1, 2021). However, if you edit the post, the datepicker will have the current month & day with the last 4 digits of the timestamp in place of the year(09/10/4400). This odd date issue also pops up when adding the metabox as a sortable column while browsing all posts of the post type.

I have also tried changing these to text_datetime_timestamp and get the same messed up dates in the back end.

Here is the code we use to set up the metabox:

$cmb_schedule->add_field(array(
    'name' => 'Class Start Date',
    'desc' => '<strong>Required</strong>',
    'id' => $prefix . 'class_start_date',
    'type' => 'text_date_timestamp',
    'attributes'  => array(
        'required'    => 'required',
    ),
    'column' => array(
        'position' => 2,
    ),
));

Thanks for taking the time to look at this for me and (hopefully) telling me where we screwed up.