Questions about the Heroes 4 map editor.

"the castle would be passed via script"

Color assignment is likely the issue.

Here's the script:
Sequence -> set the numerical variable "pandora_medium_bonus_type" to a random number within a range -> if pandora_medium_bonus_type=1, then -> sequence -> set the numerical variable "pandora_medium_bonus_monsters_lvl3" to a random number within a range -> if pandora_medium_bonus_monsters_lvl3=1, then -> sequence -> display a message + spawn monsters + remove this object.

The problem is that in most cases, everything works perfectly. The first variable has 8 variations, and the second variable has 7 variations, with 19 cases (all monsters are level 3). And then, on the last monster, on the last action "remove this object," after clicking all the "OK" buttons, the entire sequence with the 7th variation suddenly disappears.
What is the problem, and what should I do?