Whats App strange "Last seen" behavior

This is something that I have just started seeing in the last week or so. My wife's last seen time will change. For example, this morning it said "Last seen 6:52am" Then I saw her come online at 6:57am and again at 6:59am. It said "Last seen 6:59am". I go check her "friends" last seen time and it says "6:52am". I go back to my wife's last seen time and it is back to 6:52am.

That could possibly cause this?

Thanks!

It just happened again. My wife's said last seen at 709am . Then it said "last seen at 8:06am"

Her friends said last seen at 8:05am but now it says last seen at 7:59am.

My wife's reverted back to "last seen at 709am"