Should these issues be grouped under user stories / child tech tasks and be accounted for within the sprint process?
it depends (how big and how critical these bugs are)
if the item is big enough (critical bug and fixing will require to modify lots of code) then it looks like a story (or even epic)
inon the other hand - you might have munchbunch of smaller independent items - just put them all into "active bugs" box and work on those when you have time