space in a contact area between 2 teeth where there is a crown involved is either due to gum disease which causes drifting, or a poorly adapted crown. in either scenario, food impaction can result, which indeed causes a localized infection (oftentimes chronic) which leads to breakdown and pain in the tissues around the tooth. i'd get an opinion from a dentist other than the one who did the crown.
If the contact between the crown and the adjacent tooth is open(food impaction area)then this has to be corrected. When you floss and there is no resistance then this is definitely a problem.