Laptop display not correct after disconnecting external monitor

Question

I alternate between closed-lid operation connected to an Apple 23" monitor and normal open-top laptop operation. In both set ups, I am using the maximum display resolution - 1680x1250 for the Apple display and 1920x1200 for the laptop display.
After the recent Apple software updates, a problem has now developed that all the menu items in the top right hand of the screen are gone when I switch back to open lid operation. This is intermittent, but seems to hapen most times I switch back.
To get the menu items back, I go into display preferences, select a lower resolution and they all come back. I can then switch back to 1920x1250 and everything is back to normal.
Any ideas how to stop this problem from occurring would be appreciated.
TIA

Answer 1

Reset the NVRAM:
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on the computer.
Press and hold the Command-Option-P-R keys before the gray screen appears.
Hold the keys down until the computer restarts and you hear the startup sound for the third time.
Release the keys.