The fix for this (at least what I needed to do) was each item in a ticket is held in ost_thread_entry this has a field called 'Body' which actually holds the HTML by default it is of type 'TEXT' which has a max size of 64K.Change the field to 'MEDIUMTEXT' which has a max of 16MB, and this will prevent anything over 64K being cut off and causing this weird issue.