Q: Volume control keeps logging me out

Hi there EeSsCc,

Appreciate the information regarding your MacBook Pro logging out when you adjust the volume using the built-in keyboard after updating to OS X 10.11.5.

Resetting the PRAM is a great first step. To move forward, there are a couple of steps we can take to isolate whether this is a user-specific or system-wide issue:

1) Try starting your Mac in safe mode. You can check out this article on what safe mode does, what it means if an issue doesn't happen in safe mode, etc:

Try safe mode if your Mac doesn't finish starting up - Apple Support

https://support.apple.com/en-us/HT201262

2) If the issue still occurs while in safe mode, the next best step would be to create a temporary test user to see if the issue persists. If the issue appears in the test user, that points to a system-wide issue, which means that reinstalling OS X is the best course of action. Here are the steps for creating a test user:

How to test an issue in another user account on your Mac - Apple Support

https://support.apple.com/en-us/HT204443

As mentioned previously, if the issue persists in both safe mode and in the test user, you'd want to reinstall OS X. Prior to doing that, it is recommended to ensure you have a recent backup. This resource covers those two steps:

Use Time Machine to back up or restore your Mac - Apple Support

https://support.apple.com/en-us/HT201250

How to reinstall OS X on your Mac - Apple Support

https://support.apple.com/en-us/HT204904

Best of luck and thank you for being a part of the Apple Support Communities!