The flow looks ok. I don’t think the cause of the delay is in Heimdall or your flows, but somehow the disarming on the keypad is not processed in realtime in Homey. This can be because either the CPU is overloaded, too much memory in use or a delay in the Z-wave network.
You can add a notification card to the flow to get a notification on when the flow is actually executed, I suggest using Pushover for that.
