We get topics marked as having new content when they don't. Is getting a like on a post "new content" and is this the reason?
Probably because of this:
<!-- Performance optimized by Redis Object Cache. Learn more: https://wprediscache.com Opgehaald 5341 voorwerpen (6 MB) van Redis gebruikt PhpRedis (v5.3.3). -->
1. Make sure the forum page is excluded from your cache plugin, more info: https://wpforo.com/community/faq/wpforo-and-cache-plugins/
2. Click the "Mark All Read" button in the forum footer
I use the Redis because the forum was terribly slow and now it’s somewhat acceptable.