I have similar troubles with the scroll lock key. Specifying it by name does not work, I have to use the scan code.
I also found that the scroll lock key has the same scan code on two different machines. (SC046)
Try replacing ScrollLock with the scan code.
For example, the scan code is used like this:
^SC046:: ;046 is the key for Scroll Lock on my machine, where scroll lock key doesn't work when called by name.
Take a look at the special keys section on how to find the scan code:
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