The device shouldn't be behaving like that. It sounds like the update to the latest OS version has corrupted in some way.
I hate to sound like technical support, but de-registering and re-registering the device should resolve it by giving you a clean version. I had similar issues, and this worked for me.
The downside is that you will lose anything you have sideloaded to the device, and will have to re-download apps and set up logins, passwords and bookmarks again.
So once your content is backed up on your pc, and apps are backed up (if the developer offers you the option) tap settings cog>All Settings>Device Information>Erase & Deregister Device and confirm that this is what you want to do.
The device will then be as was out of the box, and when you register the device to your B&N account, your B&N content will all be there. You then need to manually add the rest of your content.
I have had my HD+ since May and have not had these problems at all. Mine works beautifully. We actually have 3 in our household and have no problems. I do recall when I got the first one, which was a 16g, that there were a few quirks with the wifi radio and a couple other minor glitches. I ended up buying a second one in the 32g storage size and passed the 16g to my son. He erased and de-registered it to set it up for himself, and that fixed it right up.
I know what a pain that is, but I would try it and hopefully you will end up loving it after that. Good luck!
Thank you so much for the replies !! AlbionRose is spot on with the solution. It has sorted out the majority of the problems. The tablet is so much smoother, feels as if its a completely different tablet.