If pages are cached, then the wrong user's vote (or lack of vote) may determine whether the "thumbs up" or "thumbs down" icon is highlighted when the page is built.
With Drupal 8's dynamic cache, this may be a problem even for authenticated users. If anonymous users are allowed to vote, then this problem comes up when using the internal page cache or an external one, like Varnish.
One solution would be to use an AJAX callback to get the correct user's voting status. I think the Big Pipe module supports this. High-traffic sites might not want to use this solution, since the point of caching is that they want to avoid bootstrapping Drupal on every page load.
A simpler solution is to offer a configuration option to disable checking for votes when loading a page. This means that there would be no visible clue when a user returns to a page that he or she had previously rated. The highlighting will still appear when the visitor votes.
Fixed
1.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Issue #2848221 by benjifisher, Prashant.c, adriancid, lobodacyril: Add...
Automatically closed - issue fixed for 2 weeks with no activity.