Spontaneous double first names in contact list

[mattwolfmatt]

I have my wife listed as "Betty" (not her real name) in my contacts. This way I can voice dial her as "Call Betty" instead of "Call Betty Jones". So she has a first name but no last name. She is listed under the "B's".

Several times in the past her name has spontaneously changed to Betty Betty (First Last). I then delete the last name, then everything's fine again. Then a couple days later it returns: Betty Betty.

Here's my setup. I have sync automatically on all three devices: iMac, MBP, and iphone. All are running the most latest software version.

Any ideas of what the deal is? I've had the iphone for 9 months; this has just started in the past 3 months or so.

Thanks!