Shape Key Drivers

Hi!
Every time I assign a driver to this particular shape key, the shape key value automatically sets to 0.0000003. When I try to adjust this value on the shape key tab, Blender notifies me that "Can’t edit driven number value, see graph editor for driver setup.
This miniscule value might seem negligible, but sometimes the value might skyrocket. I made sure that when I assigned the driver to the shapekey, the shape key value is always at 0.
Here’s what I did that didn’t solve the problem:

Reset the driver bone back to rest pose but didn’t fix.
Remade the driver from scratch but it didn’t fix.

Here are some photos of my driver and shapekey setup:


Thanks!

EDIT:
problem solved:
Since I’m using Rigify, I went to check “auto-run python scripts” in user preferences>files. Not sure why it would cause problems especially if i’m not using it actively

Nevermind, problem was solved.

Since I have Rigify add-on enabled, I checked “auto-run Python scripts” in User Preferences>Files. I’m not sure why the add-on would cause problems especially if I’m not using it actively, though.
I feel like a colossal idiot now XD