Ruben is correct. SU25’s latest feature of purging unused items is too aggressive and purges tags also. Once I checked the box for “Ask to Purge All on Save the problem when away. This can be found under Settings/General.
I checked it then I was prompted when I saved again and as to whether or not I wanted to Purge Items. I checked No and Don’t Ask Again. Now the check box under General is unchecked but everything is working okay without any magic act of making things disappear.