Anyone know why Marlin wouldn't read the endstops correctly?

[626Pilot]

I bought a Deltaprintr through Kickstarter in 2013, and it arrived last week. It's an interesting little printer. Unfortunately, they decided to use Marlin firmware, and for some reason it just doesn't read the endstops right. The controller is an Azteeg, so I'm already wary it may be hosed.

The config is weird. They have three FSRs ganged together and hooked up to the heated bed temp port, and they use that for Z probing. Other than that, they have normal endstops at the top of the towers, just like any Rostock. I used a continuity tester to verify they're all functioning right, but when I type M119, the results are straight up bizarre!

This is what it says when the Z MAX (not min!) endstop is pressed:
21:54:32.865 : x_max: open
21:54:32.865 : y_max: open
21:54:32.868 : z_min: open
21:54:32.868 : z_max: open

This is what it says for all other combinations (X pressed or not, Y pressed or not, and Z not pressed):
21:54:36.976 : x_max: open
21:54:36.978 : y_max: open
21:54:36.980 : z_min: TRIGGERED
21:54:36.980 : z_max: open

So, X and Y will report open whether triggered or not; and if Z max is triggered, it makes Z MIN say open instead of triggered. This makes absolutely no sense to me. I flipped the endstop connectors around to see if that was it, but it made no difference.

Any ideas would be appreciated!