Xlock's DPMS-suspend stops working with a few days of uptime

[ZeiP]

Xlock works fine for me most of the time, but in some point (lately it's been a few days uptime) it starts failing on putting my monitor on stand by as it's told to by the shortcut's binded command (xlock -allowroot -echokeys -dpmsstandby 5 -dpmssuspend 10 -dpmsoff 15). Any ideas on why this is? ps aux shows always in this situation a <defunct> xlock, but I haven't even once done anything too abnormal with xlock -- I just give it the password and it shuts down.