some imported posts not showing on single post pages

I imported several thousand posts in to a site I’m working on and some of them — not all of them — seem to have a problem showing on the single post page. This site has a coming soon plugin in place, so I’ll include credentials in the private content here.

So, for example, https://www.waternewsnetwork.com/water-currents/ shows a bunch of these imported posts — if you click on their titles (don’t click the full story buttons; those are external links), you’ll see that about half of them show a working post page and the other half show what seems to be a broken post page (example screen grab https://www.evernote.com/shard/s320/sh/a57f9fc5-e119-47dd-8a77-87005a4c8496/dffe4b73c0357b13e170e839d2dd8812 ).

There doesn’t seem to be any rhyme or reason as to why some are showing and some aren’t. The ones that are mission on our site show without issue on the site from which we imported them. For example https://www.waternewsnetwork.com/giant-rosarito-beach-desalination-plant-celebrated-in-groundbreaking-ceremony/ — one of the broken ones on our site — shows fine on the site from which we imported it:
http://watercurrents.sdcwa.org/2018/03/24/giant-rosarito-beach-desalination-plant-celebrated-in-groundbreaking-ceremony/

Any clues for us? Thanks!