Issues with email sent on escalation

Infos:

• Used Zammad version: 6.3.1
• Used Zammad installation type: package
• Operating system: Debian
• Browser + version: Chrome

Expected behavior:

Create a trigger to send an email when a ticket escalates

Actual behavior:

Email is sent multiple times (2 or 3 times) each 5 minutes apart.

Steps to reproduce the behavior:

1. Create an SLA with 15 min on update time:
   

2. Create a trigger to send an email on escalation (Used the created at trying to avoid it to be sent multiple times and leaving it time to be sent 1 time):

3. It will trigger up to 3 times before the 30 min is reached:

I am not sure why this is happening, tried also putting Escalation_at has changed along with Escalation_at has reached but it stopped working at all. Does anyone know how can I set this up to be only sent one time once escalation time is reached?

Best Regards,