bluetooth keyboard and mouse not connecting - LED double flashing

Hi all

I have an intermittent but recurring problem with my Macbook Pro not connecting to bluetooth keyboard and mouse. When the problem occurs, the LED on each is double flashing. Powering off and on the keyboard and mouse, or toggling off and on the bluetooth on the macbook does not solve the problem. Sometimes when this happens, bluetooth will not toggle off in system preferences. The bluetooth OFF button seems unresponsive but then when you reboot it starts up with bluetooth turned off. A reboot of the macbook fixes the problem straight away each time but then the problem comes back. I am using the macbook every day and it would happen at least once every 1-2 weeks. I have tried a PRAM reset a few times but this hasn't made any improvement. This has been going on for a few months now. It seems to make no difference whether I am at the office (with many other bluetooth devices around) or at home where there are no other bluetooth devices other than a few iOS devices.

Macbook Pro (Retina, 15-inch, early 2013)

OSX 10.10.5

Apple Magic Mouse and Wireless Keyboard