digital inputs lag 0.5-1.0 second before registering change

It appears as though there's some sort of buffer or something on our digital in's...
We noticed that our banner sensors had a 0.5-1.0 second lagtime in registering the change from a 1 to a 0.
Then we took a pwn cable and shorted out the white to the black, and noticed the same phenomenon... in other words, it's something in the programing or the RC hardware.

for testing, we were using...
- default code

- a printf statement in user_routines_fast.c, in the function where it says to put code you wish to be executed every program loop (I don't remember the function name... but it was second to last I believe)

- rc_dig_in01 and rc_dig_in07, same thing happened on both

We'd connect black to white, and watch printf keep spitting out 1's for about .5 to 1 second, then it'd go to zero. Disconnect, watch 0's print out for .5-1.0 secs, then change to 1.

What is going on???