(random thought) Given that - judging by this documentation - watchlist entries come from the recentchanges table, I wonder whether this is/could be related to T364245: Recentchanges and cu_changes tables are occasionally missing revisions on multiple wikis?

In T395629#10870153, @A_smart_kitten wrote:

(random thought) Given that - judging by this documentation - watchlist entries come from the recentchanges table, I wonder whether this is/could be related to T364245: Recentchanges and cu_changes tables are occasionally missing revisions on multiple wikis?

When I do a search for this revision select * from recentchanges where rc_this_oldid = 1292965117; , I get 0 results.

https://quarry.wmcloud.org/query/94311

I agree that this is a recentchanges data persistence issue rather than a watchlist-specific issue.

By the way, speaking personally — @TechnoSquirrel69 @Thebiguglyalien: thank you for reporting this issue! Especially with a potentially-nebulous issue such as this one (where entries are sometimes missing from recentchanges, but without an immediately clear pattern/cause), it IMO really helps to know that a previously-reported problem is still ongoing (and hasn't, e.g., been fixed by something else since the original bug report was filed). Thanks for taking the time to open a task about it on Phab :)