If not always setting it to true, it's toggling it. Once on then off then on and so on,
I modified code and set value based on boolean variable but had same issue.
custom_checkbox = TR(LABEL(), TD(INPUT(_name='agree',value=session.dummy,
_type='checkbox'), LABEL('Some setting')))
settings_form[0].insert(-1, custom_checkbox)
on form accept
session.dummy =(not session.dummy)
