Post-login automation adds garbage

[haarp]

I have a line in post-login automation, but isntead of sending the proper line, it randomly adds garbage to the end of it. The garbage changes. Roughly every fourth attempt at logging in successfuly executes my command.

Example: I want to execute this after logging in:
exec su -c ". /sdcard/login.sh"
It does this:
exec su -c ". /sdcard/login.sh" 4;89R