First of all, were you using the thermometer on the door? Generally those thermometers are not reliable and can show some widely variant temps. The assembly instructions have a method of calibration for that thermometer. And I always use a remote thermometer which I know shows true temp.
Then, was the water pan in place and full of water? The water pan acts as a thermal flywheel and moderates temperature.
If your smoker was really at 235F it should not hurt you too much since it is only 10F above what most consider the best temp of 225F. But as srmonty suggested you really need to calibrate your door thermometer and I suggest purchasing a couple of thermometers to monitor your meat that is being smoked. There is a section on this forum where thermometers have already been discussed in detail.
I actually do have a digital thermometer that I was using to take the temp inside the smoker. I also did have water in the pan as suggested in the instructions. I have not checked to see if the digital thermometer is correct or not by sticking it in boiling water. It as reading a temp about 10 to 15 degrees higher than the thermometer on the door (although I'm more inclined to believe the digital). Of course the instructions say to season it on "Low" at around 140 degrees. Not sure how you could do this based on what I've seen.
Mine said that too but throw in some ribs and the temps drop.......someone posted that to me and it came true....my reading prior was in the 250 range and after seasoning and cooking ribs I had to put it up some to get the 225 range.
As soon as you throw in a couple hunks of cold meat the temps will drop. Another thing to do is to open the vents as wide as they will go, and that may help to drop the temp. My GOSM has two vents on the sides near the bottom, and one on the top. I find that I need to open them late in the smoke when the meat has come up in temperature.
OK. Ribs, chicken and a fatty. I got rave reviews from the better half (who's a tough critic of BBQ). By far the best ribs and chicken I've ever done. I didn't brine the chicken - did halves and tooks them off at 165. Used the 3-2-1 method for the ribs. I'm a happy camper!!!