At times the triac misfires and stays ON when powering up the PCB, is it a damaged TRIAC or is the OPTO (MOC3023) underated ?
Hi,
Please post you code.
Have you measured the voltage on the output at D10 cathode, to check if its the Mega output locking on or the Triac locking on?
If you remove the optocoupler to the Triac gate does the fault still occur?
What is the load you are controlling?
Thanks.. Tom.. 
Thanks TOM. This was actually for a friend of mine whom i had designed it. It seems to be working for me just not sure why it was acting weird for him.
The load is inductive, a microwave transformer.
Hi,
Does he have it using long leads, is it for a modified transformer for spot welding?
If it is there is a thread on here that is monitored by the guy who designed one.
Tom...
Thanks TOM.
Is it Albert Van Dalen about his post here
Hi,
Yup thats the one.
Tom..
So it wasn't the triac driver. Would it be the triac then ? Checking that as well.
Hi,
If the fault was still there after removing the opto, then it would be worth a try.
But check if the projects mains power supply is good, as well as the leads and gnd.
Have you tried it back in your location?
Tom..
Mine works without a problem. Will ask him to check the triac as well.
Well it was the 8A triac. Replaced it and it is working now.
Hi,
Good to hear, thanks for the SOLVED edit.
Tom...