I can confirm that the problem reported in my previous message has gone away and those two uploads have now appeared on my watchlist. Thanks to the developers for fixing it.

I can report two further occurrences of this bug. The following two uploads should have been shown on my (User:Tokfo) watchlist on the basis that Category:Photos by User:Linie29 is on my watchlist, but they weren't:

I can report that, for me, this seems to now at least sometimes work again. (I have no way of knowing whether my watchlist is missing anything.) This upload was shown on my watchlist as an addition to "Category:Photos by User:Linie29", as it should. I don't know if this is a bug that happens sometimes but not always, or whether the code has changed, but I thought this would be useful information.

I think I just experienced the same issue as this.