This started on July 27, 2020 for me. My displayed edit count on my profile on some wikis still currently on the legacy platform (not the UCP) like Encyclopedia SpongeBobia or Big Idea Wiki (the latter of which I am a bureaucrat / admin at) is behind my actual edit count.
Has anyone else been experiencing this problem lately?
The displayed edit count is subject to caching so it does not update with each individual edit. That said, it seems Fandom has been having issues with caches not being refreshed frequently enough since about a month ago.