Sort on ticket number not working anymore

Sort on ticket number not working anymore

Hi all,

From time to time i open the default 'all open ticket' list.  Until last week i was able to sort the list on ticket number.  Now, the little icon 'arrow down' isn't shown anymore so it's impossible to sort the list on ticket number.

We can select this sort option on all other fields in the list (table view).

any idea's ?