I was able to reproduce this situation on the demo site as well. If you check it out, for the single dropdowns (the first one called modedepaiementenpersonne) we have 5 choices (Cheque-default, Interac, Argent, Employé, Autre). If you check the order, click edit, select Interac (for instance) and save it, it will save it as Interac. If you re-edit the same 'Additionnal information', the popup comes up but this field is set back to the default value which is 'Cheque'. This is the issue as it should have came back with 'Interac'.
As for Hikamarket, if I enter values with the Frontend Edition of Hikamarket, I click save and values don't save. I can't try it on the Hikashop demo site as it doesn't have Hikamarket Frontend.