Reddit Link Thumbnail not Showing Dynamic og:image
Solution 1:
Reddit caches the OG image on the first request, as do a few other services like Twitter.
Twitter offers an OG testing tool to bust the cache - Reddit does not offer such a tool.
Unfortunately, your OG image is cached on Reddit for as long as they want to cache it or until they release a tool. However, it's been like this for a few years, and it doesn't look high on their priority.
A workaround is to change the URL for the page. For example, adding a trailing slash, query param, or renaming the route.