Hi Jonathan,
Thanks for taking the time to reply :-)
I kinda suspected that 60 characters were the limit ... which is quite a shame to be honest .. The field I am referring to is a kind of long, unique article description ... having the enhanced search enabled gives the user some idea of what exists already ... so essentially it is an aid for the user to prevent typing in the same value again ... ( not exactly the purpose of an auto suggest search help ofc ... if that makes sense 
). Having a limit of the actual length of the field sounds kinda weird to me ... seeing what advanced built-in text analytics & mining capabilities HANA has ...
I noticed that the 'weird' search result return is actually apparently influenced by the customer search exit I used ... once removed I was receiving again a narrowed down list with only the results matching the entered word ... so it seems the custom exit was counter working the hana search ...
But unfortunately I have to indeed disable the search help as - when enabled - the user cannot use the full allowed text width to type in new values ... which is not what we intend ofc ...
Thanks,
Steven