I am not seeing that lag. Have you run your instance in debug mode to see how fast the messages come in? It would be helpful to know if the message are the bottleneck or if Home Assistant is the bottle neck.
From what I can see, the delay seems to be with the messages. Running a tail -f on the log file I only see messages as the state change occurs. If I look at my Insteon repeater the state change occurs as the message light stops flashing and reverts to static, which is why I made the assumption that the logic was waiting for all of the messages to come in as opposed to executing on the first and then ignoring the subsequent ones.
Is there any specific testing or logging you’d recommend?
Can you send the debug log with both /homeassistant/components/insteon_plm and insteonplm both in debug mode? Here is the configuration.yaml settings you need:
logger:
default: warn
logs:
insteonplm: debug
homeassistant.components.insteon_plm: debug
A breaking change is expected to happen for both insteon_plm and insteonlocal. Please see this thread and give your input: