When you recive a notification and open de "mail symbol" you have two opcions: 1- Mark as read, swiping to the right and push the option 2- Delete, swiping to the left and push the option.

But, when you sliding to any side you can´t return de movement. You can do that, only if you leave the notifications menu.

It should be possible to return to the action without having to leave the notification menu.

In this link, is the video that shows this problem