Its wood, it expands and contracts, different pieces will mave independently of each other and unfortunately you cannot stop nature.. It will get worse for certain. If you wanted perfect wood was not the choice you should have made.

It you wanted plastic cabinets, a high end custom cabinet wasn’t your best choice. Wood behaves like wood, and the only way that you can stop it is by museum level humidity and temperature control.

They did tell us we could expect hairline cracks due to the wood expanding and contracting. That's just not what I expected it to look like. To me it looks like the joint wasn't properly filled before being painted, like mentioned above. But I'm no cabinet expert which is why I was looking for the opinion of professionals. Thank you

Some of my maple wood cabinets are starting to get hairline cracks after almost 2 years but none look like that. I agree that looks more like a manufacturing oops especially if they were just installed.

Yes they are new. They were just installed last week.