Share your experience!
Hi,
That sounds strange. Do you have many messages in general? For example, messages that you imported from another phone or similar?
If you have choosen to import the messages from your iPhone, it will import all the messages. Could you take a look in the following thread to see if any of my advice can help you in this matter?
http://talk.sonymobile.com/t5/Xperia-Z1-Z1s/Messaging-app-problem-after-lollipop-update/td-p/999160
Let's try this
settings > apps > all > messaging > clear data > force stop > restart the phone > try again
if that doesn't work then
Boot on safe mode and try again
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008
the last resort will be to repair the phone with PCC
Bridge (for Mac)
Alternatives on How to backup Xperias
http://talk.sonymobile.com/thread/36355