Rematch: Rematch_5_1_4.zip
Pet Battle Scripts: PetBattleScripts-v1.10.1.zip

When I click the test button multiple times, only the first line of instructions is executed.

Note: I only enable Rematch and Pet Battle Scripts addon, but the problem is the same.
I copy some sample script from https://www.wow-petguide.com/ to double check. The problem is the same.
How should I debug this?

Thanks

Scripts run from top to bottom every time you press the button. The first action that can be executed based on conditions and cooldowns will win and end the script. I would assume your first line can be executed unconditionally, so it is executed unconditionally.

Care to post the script you're using?

I use this two skill and only top one will be executed. No idea why the next one didn't be effective

Ability 1370 has no cooldown and you didn't give it a condition, so it will be always executed, as said.

I assume your script is supposed to keep 919 debuff active and otherwise spam 1370. To do that,

use(claw:919) [ !enemy.aura(claw debuff:918).exists ]
use(filler:1370)

or if you want to have the filler in the first and only first round as well,

use(filler:1370) [ round = 1 ]
use(claw:919) [ !enemy.aura(claw debuff:918).exists ]
use(filler:1370)

Thank you for patiently explaining, I understand now, I have no more questions. I really appreciate your help.