Keyboard misbehaving!

I have a Logitech K520 keyboard/mouse combo, connecting to my PC by Bluetooth via a tiny dongle. Firstly. Quite inexplicably, @ and " have for some obscure reason, transposed themselves. I always have to press one to get the other. Both symbols are Shift typed. The non shift 2 and ' on the same two keys, work perfectly normally. And now my Alt Gr has stopped functioning altogether! I do prefer my Latte and Pate to be spelled correctly!
I don't honestly expect anyone to solve the problem. Just having a moan, really!
I would first check another keyboard to see if the problem is still there, and I have read , while researching keyboard problems that if you have a ps/2 keyboard and go to a usb keyboard, sometimes the usb keyboard will have partial problems with some keys.
Bit of a delay in answering, due to family considerations. Would you believe it? I had a perfectly good, working usb keyboard that I gave away to a charity shop about a month ago! Always the way.
I believe that is one of the laws of nature, :)

You will never need something as much as the item you just threw away.

Never say never, you will find yourself doing the same action again.

:) :)

Have you found another keyboard to test the issue with?