Invoice date missing

Hi all

I suddenly noticed that the invoice date is missing on the PDF invoice. It used to show the date until about 2 months ago.
Settings are double checked, and the preview (in settings) is showing the invoice date correctly. Only when I click the ‘regenerate’ button (after the original invoice is created) the invoice date is added to the PDF invoice.

As I’m also using the Dropbox backup this is very annoying because I have to regenerate every invoice, click the invoice button and download it to Dropbox to overwrite the original invoice.

Does anyone have a clue?

Many thanks!