You’re not alone.
This update has made a mess out of thousands of sites that relied on Jetpack to deliver images with VISIBLE descriptions.
It’s a new “feature” of the “improved” Carousel. By default, it now hides your description and “View full size” link.
You can provide access to these by going to:
Settings / Media / Image Gallery Carousel
And checking the “Metadata” box (Show photo metadata (Exif) in carousel, when available).
This isn’t ideal, because now visitors need to click the information icon to view your description.
Unfortunately, the folks at Jetpack don’t seem to really care that you spent hours writing image descriptions, that no one can now read.