For those with potential footswitch issues straight out of the box, just try 'exercising' the switch rapidly through 50-100 presses and retest before drawing conclusions (much quicker if done by hand and easy to push as they're momentary). I say this as it resolved my issues with switches 4 and 5, which now behave perfectly. I suspect switch contacts have not been actioned much/at all because they are new will be generating some switching noise. If it was part of an analogue circuit, you'd hear the noise in the signal. If this is switch is just being interpreted as binary the noise on that signal could mean it doesn't reliably send 0 or 1, either not triggering or double-triggering on/off. This seemed to be the behaviour I had, and it quickly went away. I don't think this is poor quality componentry per se, as this is common to all electro-mechanical switches/pots/faders including those on new large-format mixing consoles I commission that just need to be used.
If it's still broken, it's broken, but I'd give it a go first if it really is straight out of the box.