I'm a kitchen designer at a custom millwork manufacturer.
Wood vs. MDF custom painted cabinets?
We are located in Canada where the climate change is quite significant from summer to winter. We use MDF on 9 out of 10 painted kitchens because it's engineering makes it a much stronger product that doesn't expand opinion contract in the same way that solid wood does.
We will paint on solid wood but strongly discourage it due to the cracking that can occur both blog the seams and between the rails and panel. It's kind of a scary idea when you're spending several naked swimming of dollars on naked kitchen!
I also strongly recommend MDF kitchen I've never seen a door from our company that "falls apart". I'm wondering if cabinet is a bigger issue with low doors cabinet makers.
Kitchen Cabinet Construction
This may also be an issue with your door joinery. A cope and stick joint is always the strongest, and a miter corner joint is best if done by a high end machine that can build good finger joints.
We also use a catalyst based spray paint which has strong hardening agents - I'd wish you good luck to try to remove it!