Once the automation has been triggered, does it start to correctly increase the brightness and then never stops increasing or does it increase once and then it stops?
I think even if you manage to get this to work, it’ll still not work as intended, because the brightness_step_pct part needs to read the current brightness before it adjusts the brightness and the next increase comes before the first increase has been finished, therefore HA is not able to read the correct current brightness. There’s an appdaemon app called Controller X that has a workaround for this issue.