I’m sorry to hear about your door problems. Wet weather can cause issues for doors that weren’t necessarily designed to be exterior doors and if you think about the front door on your house, it’s likely to be much more weatherproof than your yurt door. Make sure to site your yurt with the door facing away from the prevailing weather to reduce this issue but the best solution to your problem is to protect your door with a porch. On a practical level, it’ll keep the weather off and stop it swelling and aesthetically, a nicely shaped porch can add to the look of your yurt. It can be anything from a simple canvas porch that is easy and quick to fit, to something you design and build yourself. Good luck.