Pulling extract instead of Alt Text for Pinterest image

I’ve just loaded a new install of WP and Mantra on a new site having been a mantra user for several years. There are only a couple of posts but this problem has me stumped.

I set a featured image for each page or post, but when trying to Pin the featured image, even though it has a title and alt text set, those are being ignored and the pin text is the full text from the article, which is silly and wrong!

It should pick up the Alt Text of the image for the Pinterest description. I’ve been through everything and just can’t work it out. Anyone have any tips or solutions please?

See it at https://debycoles.com