Question [Q] Long SMS issue ?

Hi all ,

Hope someone has a simple fix that im missing here

My partners phone is the S4, its not rooted and has everything stock ! However more recently shes been sending me texts and im not getting them - we have managed to narrow this down to "long texts" not being sent, the shorter ones come through just fine. Shes using GoSMS as am I as we can easily send pics via the GoSMS app without it becoming an MMS .

Below ive tried

Using Stock SMS app, Clearing Cache/data from GoSMS
Google'd it , however the problem doesnt seem to come up anywhere ( thats useful or appropriate )
Changed settings within GoSMS ( handling of notifcations ect if stock sms is present )

Its driving me insane ! Has anyone come across this issue ? Shes on EE network here in the UK

For anyone who does or can help , thank you in advance !

Samsung Galaxy S2 8GB
Samsung Galaxy Note 2 16GB
Samsung Galaxy Note 3 32GB (n9005 )
RIP KNOX 0x0 & 4.3 BL ----> <---- This is why I Love KitKat