Exor HMI problem

I have an exor eTOP33 HMI and I finding I am having problems when trying to input a numeric value. The problem is when I input a value, The address in the PLC processor is changed but sometimes the new value seems to be pasted on top of the old value on the display so you can't read the value you have just entered. if you change the page and come back you can see the value as it should have been the first time.

Has anyone else come acrss this problem or I am doing something stupid?

Thanks in advance.