Strange behaviour from Call Service Node

I'm looking for a bit of help with a simple but annoying issue.
I am controlling a 4 gang Zigbee switch (it's a bare board TuYa TS0004).
It works fine except for the first time I trigger the flow (it's triggered by an Alexa-Home node) .......
When initially triggered I get all the correct debug messages from Node-Red but nothing happens at the switch. I have monitored the Zigbee2MQTT logs and can confirm no message arrives from the trigger.
If I then re-trigger, everything works perfectly, exactly the same debug output from Node-Red as before but this time the messages are visible in the Zigbe2MQTTlog and the switch toggles
Anyone got a clue what might be going on here ?

Welcome to the forum @nick4275

Unfortunately your question is much to vague to provide an answer. However, if it is specifically a home assistant node that is giving the problem then you will probably need to ask on a home assistant forum. Few here use HA, preferring to do everything in node red.