The switch has to go only until it moves enough to make contact. If it did not make contact, you would get an alarm.
Sounds like a short somewhere in the switch cable or a control defect/error. First I would go into setting graphics and disable the tool release button on the panel, just to make sure the button on the panel is not bad and making contact by itself.
Then check the wiring and the switch on the column to make sure it is okay. Have to admit, I have not seen this before. Remember that there are only a couple of modes where the tool can be released in the first place, MDI and JOG that I can remember right off the bat.
It should not be able to do a tool release during a program and if it does, it would be a serious control issue.
Mike