didSelectRowAtIndexPath returns wrong row index inconsistently - ios

Question

I have a table view with rows, and when clicking on the row, sometimes it returns the row that is up one position from the one I clicked. The relevant code:
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let currentCell: UITableViewCell = self.tableView.cellForRowAtIndexPath(indexPath)!
currentCell.backgroundColor = UIColor.greenColor()
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell:UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("cell")!
//.... cell modifications
return cell
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// this is to make at least one empty row
if (meeting.attendees.isEmpty) {
return 1
} else {
if section == 0 {
return requiredParticipants.count }
else {
return optionalParticipants.count }
}
}
What did I do to address the issue:
1. checked the consistency of arrays with the numberOfRows function (it's correct, the number is right)
2. checked the height of the cell - suspected the upper cell to overlap somehow the bottom cell - also not the case
3. refactored cellForRow to use dequeReusableCell (was not used initially) - suspected the memory issue, also did not help.
What happens: when you click, the cell that is clicked is highlighted with the green light, and approx. 50% of the time, the cell one position up from the one you click gets highlighted. The issue is also inconsistent, meaning that half of the time the right one is highlighted.