Diagnostics Health Check incorrect

I have a site on Perch 2.5.2 but its reporting as ... Perch is up to date. After upgrading to the latest (2.5.3) it reports ... Ahead of the curve! I noticed the same reporting when moving from 2.5.1 to 2.5.2 but thought it might fix itself. I think I've seen it at some other Perch sites, so will see as I upgrade them all to 2.5.3 while I'm watching the footie. :-)