Advanced date picker custom field disappeared in checkout

-- HikaShop version -- : 4.6.1
-- Joomla version -- : 3.9.28

As far as I know I haven't changed anything and all of the sudden my advanced date picker custom field isn't shown anymore during checkout. It shows the title, but no date selector.

I've checked the custom field settings and I can't find anything there. I also found one other forum post which could maybe be related
www.hikashop.com/forum/checkout/903793-a...ker-not-working.html

Edit 1:
I found an error in the javascript console, but can't solve the problem. I added a screenshot.

Edit 2:
I've found where this error came from and temporarily solved it. A few weeks ago I did a security scan for our website and it gave me a few tips for improving security. One of those was to implement CSP. So I've added the following line to my .htaccess file to enable this and now I've found that this stopped the datepicker from working. It must've been this way for weeks and we've just not noticed it.

Header set Content-Security-Policy "default-src 'unsafe-inline' https: 'self' data:; upgrade-insecure-requests; frame-ancestors 'self'"

That's strange. I completely missed your reply when I edited the original message.

I found where the problem came from, but still have a question about security.

Thanks Nicolas. I'll leave it for now.

Another thing. I want to remove the screenshots, but it wont let me. When I click "remove" or "remove all" it doesn't do anything.