screen has been dimmed, doesn't return to normal, remains dim after talkback off

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What steps will reproduce the problem?
1. start talkback 
2. check box to dim screen when talkback is enabled. screen is now dimmed.
3. end talkback service. screen remains dimmed. 

What is the expected output? What do you see instead?
I expect the screen to return to normal backlighting when talkback is turned 
off. 
The screen remains dimmed. 

What version of the product are you using? On what operating system?
Talkback V 4.2.0 on Cyanogenmod 12 with a Oneplus One device.

Please provide any additional information below.
Screenshot attached is of the dimming setting. 
Backlight remains dim on the device even though talkback has been turned off. 
The screen cannot be used normaly at all! This app has ruined my device and 
made it completely unusable. The device still functions normally except the 
backlight is set to an unusable low level. The screen can only be viewed in a 
dark room using a flashlight right into the screen.  

Original issue reported on code.google.com by griffom...@gmail.com on 30 Jul 2015 at 12:53

Attachments:

• Screenshot_2015-07-29-15-01-25.png