Intersting, just a few minutes ago I interacted in a similar issue here:
https://toolset.com/forums/topic/custom-size-featured-image-does-not-work/
There, the user cannot pull the resized image, which seems to be non-existing.
However, related to your report, I see you use a Custom Image Size that is registered in the Theme ([wpv-post-featured-image size="page-header"] ).
You mention having ensured the Thumbnails exist for that specific size for all Images, hence, the ShortCode likely should have no reason to fail.
I also tried here, to locally replicate such a scenario, but when I register a custom size with add_image_size(), where crop is true, and upload images to WordPress to later display them with the custom size using Toolset ShortCodes, it works fine.
I am confused about your second paragraph.
Do you upload already cropped, resized Images to WordPress?.
Then, you'd not need to create a new Image Thumbnail size with add_image_size() and call that in the ShortCode, you could just call the Full Image size, as that would already be the (since it's the maximum available) cropped and resized image you uploaded.
What do I misunderstand here? I am sure there is a connection between both which I miss.
Related to the fact that some pages work and some not, I suspect, there is either a setting, a difference in the ShortCode, template, or even the Image, on those posts that work versus those that don't.
As first steps towards a solution, I'd suggest also here to try without any plugins but Toolset and changing the Theme (on a staging site for safety). Then I'd suggest try to narrow down the difference between working, and not working posts if the issue persists.
You can look for templates assigned, other ShortCodes present, eventual broken ShortCodes (maybe apostrophes got corrupted, or similar).
If all this does not help, can you send me a link of A) a working page where only the ShortCode is present (if possible) and B) a not working page, also where only the ShortCode is inserted.
I can then try to narrow it down, or maybe proceed locally with a copy of your site if online I cannot see anything.
In case you want to help expedite that process, you can already create such copy (also a great tool to create Staging sites) following https://toolset.com/faq/provide-supporters-copy-site/
In case that'll be needed, you can find the Private reply mode already active on your next reply here.