Issues when correcting transactions in Sage Accounts

We have a situation where we need to go back in and update the 'Description' field on our Transactions - i was able to do this using the 'edit' process described here:

https://ask.sage.co.uk/scripts/ask.cfg/php.exe/enduser/std_adp.php?p_faqid=21428

For the majority of our transactions this works fine and the relevant information that i input, is then visible within the 'Details' field within Customers > Activity - the issue we're having is that on some transactions, i go in and update the 'Description' field, but the information doesn't seem to pull through and the 'Details' field within Customers > Activity shows as blank.

I initially thought i had just forgotten to input the information in the 'Description' field, but when i went back in, the field did have the expected information in there, but when i closed it down - the 'Details' field within Customers > Activity was still showing as blank.

Does anybody have any ideas as to why this information is not pulling through?