Cutting settings for 12mm birch plywood

I am trying to cut 12mm birch plywood. I have a W4 reci laser tube, I can get through majority of the wood, however some spots i cannot get through. I have the settings at 6mm and 80% power. Any suggestions? am i not getting enough air assist? i just cleaned the mirrors and lens. I am at 26 mA on my output reader.

More than 1 pass?
I would try moving Z down on each pass.

1 pass, I dont like to run more than 1 pass if i can help it. I have tried moving it down on the Z, with the results getting better, then it moves past the focal point and the it starts not cutting at all.

The Zaxis correction should only be 6mm to put the focal point in the middle of the material. Then hopefully it will still cut when 6mm out of focus.

You would be amazed at how many users recommend multiple passes instead of one. Total cut time reduction and a cleaner burn are often reported. There is no shame in using multiple passes.