I don't know how common it is but it shouldn't happen with any degree of frequency. Wood naturally expands and contracts, mostly across the grain with changes in humidity. Proper frame and panel construction allows for that movement. I might suspect that either the doors were not constructed properly or there's enough paint to inhibit movement.

Years ago, in my early woodworking days, I made a "test" table with a breadboard edge. Properly done a breadboard edges allows movement of the field while reducing the tendency of larger panels to cup. Well...for whatever reason I glued the edge. About a year later the field of the table top cracked and released enough energy to make a noise similar to a small caliber gunshot.

Yes, you should raise royal h-e double toothpick with the manufacturer. Frankly, there's little reason to use a solid wood panel in a painted cabinet door like yours.

Bad construction. Try contacting the manufacturer. If they don't recognize it as a defective product, they aren't willing to stand behind their reputation.

If one door split, it could be a fluke. When 66% of them split you know someone messed up.

If you can't get them to fix it then I'd suggest avoiding future dealings with the company and buy replacement doors from a reputable supplier.

The design of a frame and panel door is made to prevent the wood from splitting when temperature changes cause the wood to expand and shrink. It seems that the panel may not be free floating in the frame i.e., if the panel is fastened to the frame at the sides, as the wood shrinks it pulls the glue joint apart in the middle. What do the backs of the doors look like?

Thanks for the comments. Bluewillow, here are a few more shots of the rear of the cabinet (sorry, the uploaded horizontally). In speaking to the cabinet provider, his only comment was that it was caused by dry air in the house (a lack of humidity) and was unavoidable. It is true that our house is very dry during the winter.

Cop out. Proper door construction technique allows for shrinkage during dry conditions. Someone probably glued the doors into the grooves. They should have used plywood or some other engineered wood product if they wanted to glue them in like that.

Only sudden and drastic humidity changes should have a chance of damaging properly assembled wood and finish (or paint) mitigates that effect.

What is the easiest way for me to determine if the doors have been glued into the grooves?

The easiest method is destructive so you'll definitely lose a door. Cut with a saw from the outside corner of the door to the corner of the panel. Do that on all four corners and the two stiles on the sides should come right off. If they don't, they are held in place with glue or nails or something else.

Another option is to carefully examine the backside and look for telltale dips in the finish where nails have been painted over.

You could also ask the manufacturer to see if they give a straight answer or avoid the issue.

Did you paint them after they were assembled? Paint in the grooves that hold the panel in the frame can act as glue to restrict the movement. Agree with the others that this should not happen in a frame and panel door. A typical solid panel can move upwards of a quarter inch seasonally, the whole point of the frame and panel design is to allow that movement to happen without splitting.

No, I did not paint them after they were assembled. It has been hard for me to tell if the panel is glued in or not - I don't THINK it is, as I pressed the panel in the cabinets that had not cracked, and there was a little "give" - not a lot of shifting, but they definitely did not feel as "tight" as the cabinets that have cracks. We have a humidity problem in our house during winter, when % can get down into the mid-20s. So it has been hard for me to argue that its craftsmanship and not just an abnormally dry environment.