Hmm. After taking a quick peek at it, the first thing that comes to mind, did you change the option in the "bdsm_controls" script?
//If set to 1, the slave collars will be unequipable from the slave's neck slot
//unless their master allows them to remove them. If set to 0, the slave can
//remove them at will.
//Defualt = 1
const int COLLAR_UNEQUIPABLE = 1;
Hopefully it's as simple as that but these things usually never are.