Can't make any new invoice recently

Hey,
I’m using Dolibarr 12.0.1 (I recently upgraded from version 10 when I met a bug, and made the upgrade hoping it’d fix things. It didn’t).

When I go to “Billing | Payment” > “New invoice” the first thing weird is that, the “Now” helper doesn’t seem to work (to add the “today” date to the bill). I tried multiple browsers and computer, I have the same thing. I watched a bit into the source, and saw it was pretty easy to see a jquerry thingy saying “write AA/MM/YYYY”, so I did.
I just mention this “little quirk” because I guess it’s a behaviour I never had before, so it might be related somehow.

I then fill the rest of the page, then pushed “create draft”… And it does nothing. No error, just goes from dolibarr/htdocs/compta/facture/card.php?action=create&leftmenu= to dolibarr/htdocs/compta/facture/card.php and anything I do from there always send me back to this last page in an infinite loop. No error, no nothing.

What is hapenning to me ? I did not change anything priori to this “bug”. Now I did upgrade from 10 to the latest available release, but it did not fix things. And so here I am. You can fetch me on #dolibarr freenode if you want.

Re. Actually I just found out I lied. I didn’t think of it, but I tweaked my nginx conf recently over a discussion about “make internet safer”.
I added theses bits :

  add_header Content-Security-Policy "default-src 'self';";

  add_header Referrer-Policy "no-referrer";

Dolibarr didn’t liked them at all. At all I tell you.
Removing it fixed it.

Only

add_header Content-Security-Policy “default-src ‘self’;”;

Was responsible after all. Why ? Could you explain it to me ? Is there external jquerry stuff not slef hosted ?