When you set "walk_on 0" to a button it will never get
pressed because it doesn't realize a step-on. When you set
"walk_off 0" the button will get pressed only once and never
be released because it doesn't realize the step-off.
Kurt's proposed changes make a lot of sense, really.
AFAIK it is not possible to make a sane work-around for
the problem, and I really tried hard once.
AndreasV