When you sort by activity I can't figure out how HU is sorting but it is not by time and date. Some are sorted and are a of them that are jumbled.
Probably worth showing the headings of the table in your screenshot to confirm the sorting you are applying... It can be a little confusing when parent devices are involved but that doesn't appear to be the case for you, but like I said, I would need to see the sorting you are applying to be sure what may be happening. An example of what I am suggesting you post would be below, where you can see the Last Activity heading with the sort option selected:
If I do that you will not see the items that are missed sorted. I have sorted them ascending and descending and they are always out if order
Ok, then that is weird. Probably one for support more so than a feature request I would expect.
Something that may be relevant (or not).... what platform version are you running on your hub? i.e. if you click on Settings and Hub Details, what is the version shown in the first entry of the pop-up?
Hubitat Elevation® Platform Version
Here is a better picture
Don’t think it matters, but you might want to update your hub (unless there is a valid reason to keep it that old.)