Satan's Slime [GAME JAM]

This seems like an interesting game, but I unfortunately wasn't able to play for long before I ran into this error. If it helps, I got this error immediately after purchasing the Roomba trap and starting the next wave:

############################################################################################
ERROR in
action number 1
of Step Event0
for object o_ENEMY_PARENT:
Variable o_KNIGHT.secs(100343, -2147483648) not set before reading it.
at gml_Object_o_ENEMY_PARENT_Step_0
############################################################################################
gml_Object_o_ENEMY_PARENT_Step_0 (line -1)
gml_Object_o_KNIGHT_Step_0 (line -1)