Did some more testing, and it seems the problem is linked to "Pick lowest/Highest" when used with a family.
So it doesn't seem to have anything to do with the names after all.
The error messages are the same as shown beneath.
After the bug with the family variable, and upgrading to r164.2 im experiencing some weird errors. My game is a tower defense game, and each turret have a type in form of a string. For instant "Gun", "Energy" etc. that are a family variable. After the bug and upgrading to r164.2 it wont accept some of the names anymore. Meaning that if I type the name "Gun" in the string variable the game crashes with the same error as in r164. I then found out that if I renamed it to "Gun1" then it worked. However its only some of the towers that have this problem, for instant the turret called "Energy" I didn't have to rename. I have also tried to just give the Gun turret the type of "Energy" and then it also works. Its only if its called "Gun", or one of the other turret type names I had to rename as well, it doesn't work. I thought...
I found some code in the program that still relying on turret type to be "Gun" so to make it work again I renamed it to "Gun1" as I have done the other places, but now it crashes again with the same family error as in r164.
And its really annoying since it makes no sense that it works, (Thought it worked) if it was called "Gun1" instead of "Gun". There are nothing special about this variable. The only thing its used for is checks like these:
Turret.type = "Gun"
To me it seems that the bug have somehow broken my game.
Have anyone else had these problems?
Description of Capx
Just a turret defense game, using the turret function, nothing special.
Steps to Reproduce Bug
 Changing value of a variable.
Operating System and Service Pack
Construct 2 Version ID