The devs have said this is "intentional" ... because all traps/spikes can hurt the player.

So, unless they change their mind based on feedback ... this isn't something to be "fixed" since it is working as intended.

I've not bothered with them. I guess you could set them up so their field of fire doesn't cover the entrance. Also saw a video where they were mounted high enough the player can walk under them and not be targeted ... but that would make them basically useless against ground mobs. Thus, why I've not bothered with them.