Hey @Snox,
Thanks for your post. We're going to send this over to our Support team so they can take a look at your account and see what's going on. If you have a similar question please submit a support ticket and we will investigate further.
Curiously, I have the exact opposite.
The latest activity appears everywhere except one place - our Club Leaderboard.
Nothing has changed in terms of setup, profile or anything else.
Its just that my last activity wont appear on club leaderboards.
I even doubled it up by duplicating the activity, with one tiny change - the duplicate appeared everywhere else across Strava - except on the Leaderboard.