The notrunning condition in version r11.3 does not act as it did in 4.x. This has been addressed in r11.3.5 INC2 and r11.3.6.
Having multiple box jobs defined with notrunning condition may start to run at the same time.
Suggested workaround for r11.3:
Define multiple command jobs per each box job that can issue a “sendevent -E STARTJOB”. Use a (Real or Virtual) Resource attribute to define all the conditions on the multiple command jobs such that only one box job could run at a time.
Upgrade to r11.3.5 INC2 or r11.3.6 where the notrunning condition has been defined to operate as it did in 4.x.