Adjustment brush only lightens regardless of any setting

[Jayce]

Damien, let me start with how much I miss seeing you in my Facebook feed everyday! You are a wonderful teacher!  My question is that I am running Lightroom 5.7.1 and my adjustmet brush is only brightening where I apply on the image and nothing else. I have reset and tried to increase shadow or exposure and it just lightens.  Let me know if you have any ideas. Thank you. 

[Christina Keddie]

...Oh dear.  This is kind of like a "how many things can we throw in that will make Damien want to punch his computer" post.

So okay.  Damo isn't going to advise on LR, because he hates LR.  But leaving that aside --

You really, really don't want to be using your adjustment brushes anyways.  That kind of targeted editing should always be done in PSE, where you actually have fine-grained control of your editing.  I'd strongly urge you to stop using your adjustment brushes and instead adopt a more robust LR-to-PSE workflow.  (I've written several posts in this subforum with more details on how to put such a workflow together, and I'm happy to help you walk through it if you have any questions.)

That all said -- it sounds like your computer is glitching.  So can you fill this out for us and we can try to diagnose what the problem may be?