Yes, I believe these will resolve themselves… I think the white thumbs are the result of the page taking too long to load so the white is just a thumb of that blank screen you see until the page is loaded. My guess is the service only waits so long before doing the capture.
Honestly though… this is the first time I’ve seen this. I just checked my template demo pages and there are some white thumbs there too. So maybe there was a change in the wordpress.org service that creates the thumbs recently… my best guess as I do not have any control over the service that actually creates the thumbs.
I’ll keep an eye on it and if it seems like it is becoming too unreliable, I’ll have to retire SiteShot.