Apple A1314 Bluetooth pairing problem

I have this huge problem with Apples A1314 bluetooth keyboard.

The bluetooth keyboard pairs with the iMac perfectly. However, from now and then, the iMac looses the pairing after restart, reboot, shutdown, sleep..

It needs the pairing to be done again. But, at the login screen, you can't pair the keyboard by default. I first need to login to be able to pair the keyboard

but first need to pair the keyboard to be able to enter my password.

So, there are 2 possible solutions I can live with:

-1) How to avaid the iMac loosing the pairing with the keyboard

-2) How to be able to pair a keyboard before I must enter the pasword

Unfortunately Apple doesn't give support to its customers so I have to ask the community and I'd be very grateful if someone could help me by answering at least one of these 2 questions.

To improve the quality of these customer support forums, please don't answer things like:

- don't buy crapware

- don't buy apple

- can't be done

- it's apple, live with it being full of flaws

- any other non helpful content..

simply answer to one of the questions if you know the answer or please don't comment at all.. since these forums get full of people starting discussions and getting away from the actual question very fast and it's not helpful for other readers if they first have to scroll and read 200 posts to find the actual answer to these questions.