keithy:
I am on the arduino forum, the original post talks about the micro
There are multiple versions of the Micro.
and the MKR photo relay board so I would think that it was probably the Arduino components.
Arduino company produces the boards - maybe some shields, but there are lots of third-party components. Don't expect just anyone to expect your oblique references.
One less sale for arduino and when we go to production in 4 weeks a lot less sales
I really hope you're using much more exact references to products on your BOM for production than you use for asking questions on a forum!
And I wonder why anyone would even consider to use Arduino boards and relays on pre-made PCBs for a mass produced system. Even the clones are too expensive for that, and not likely to fit nicely in whatever product you want to make.
Furthermore, if you're NOW have answers about basic questions like how to connect stuff together, going to production in 4 weeks can only end in disaster. But that'd be no big loss for us, considering your attitude.