After update to 10.13.3, the keyboard fails to operate on OS login

I recently upgraded the software on my iMac to macOS High Sierra v10.13.3 and unfortunately, on the login screen after coming out of sleep mode the password field is not responsive on the wireless keyboard. A few mouse clicks are recorded then stops erraticlly. At first I thought it was the batteries and so I replaced them and it worked. But now it is happening again the following day and the only way to stop it is to disconnect the keyboard and reconnect. I never had any issues with this prior to the software update! The only workaround is to reboot the computer. Greg H.