Hi,
actions do no operate randomly at all, in a state each action is performed in the exact order it's setup. the sequence option only impose that the state executes each action one after the other WHEN the action tells it has finished, that's all.
what could be happening is that if you temper with array content, you may need to force saving the array before other action use it straight away, that's likely what happens with you.
check the action ArraySaveChange on the eocsystem. that could be what you need.
Bye,
Jean