Originally Posted by fred m deolick
Yes, thats exactly what is happening. The thinner strip on the back side seems to crack with little pressure on it. I've noticed that the white colored wood seems to be more likely to splinter.
Let me list a couple of things that come to mind about why that might have happened. These are in order of my best guess to just a guess.
Were all the pieces flat? If the rails/stiles/panels/ were warped or cupped things would be very difficult to line up and fit. Even dry wood has stresses, sometimes when cutting or doing other operations the board that was flat will twist. Sometimes this happens even as you are working on the piece sometimes it takes a couple of days to notice.
When you did a dry fit of the panel to a rail/stiles was the panel free to move about or very snug? The panels need to be free to move and if that was not the case either the panel needs to be smaller or the “groove” wider.
Did you take a piece of sand paper and easy the sharp edges? The panel ends are going to be hidden anyway so take a little more off on them.
If you were using clamps to pull the dry fit together they may have buckled or arched the door. Some clamps are not designed to tighten a frame together so it requires more time and extra effort to make sure everything remain flat. Light tapping helps, if you have to really hit it then something is wrong so stop.
What you might be able to do to save the work you have done is to remove the back strips altogether. Drop in the panels and use a filler strip in place of that removed strip, more like you would do if the panels were glass. That strip could be glued then tacked with a brad push nailer to the rail/stile. Make sure no glue gets on the panels they will need to move. If you don't have one of those brad push nailers get one, they are less then $10 and work great on this sort of project.