iRule events firing out of order?

I wonder how the events are supported within the F5... It's almost like some variables aren't being made available between events immediately... And if the events trigger too close to each other, then I get no such variable errors... (WHich should be impossible, because SERVER_CONNECTED is literally

when SERVER_CONNECTED {
  set s_offset 1
  TCP::collect
}

and then about 4% of the time when I sent a sudden load of about 100 connections and requests, I get TCL errors in SERVER_DATA claiming s_offset isn't a known variable...

H