If you find irregular surfaces at the glue line in wood projects, the problem can be moisture levels. This can happen, for example, when one piece has a 15% moisture content, while those next to it are at 8%. If you glue and plane boards with unequal moisture, those with higher moisture will eventually shrink more than those with less moisture.
When you take a vacation, don’t forget to give your appliances a rest too. Turn off and unplug everything you can, set your water heater to the lowest setting and shut off the water supply to the dishwasher and washing machine.