2nd batch of ribs, not as good as the first

This is my second cook on my egg. First cook turned out great juicy baby backs. Couldn't have asked for better. Everything the egg promised and more. They were so good that I decided to make more today. Unfortunately they didn't turn out as good as the first batch. They turned out dry and stuck to the bone too much. I hate having to chew the meat off the bone. A good rib should have it's meat pull right off (not fall off). I think it was a temperature problem. Set up the same way as last time. Dome temp 225F. Every hour opened briefly to spritz with apple juice/apple cider vinegar. Then an odd thing happened. In the middle of the 3rd hour, the temp rose to 330F. I don't know how long it stayed that high, but it couldn't have been more than 15-20 minutes, since I check the temp regularly. Nothing had changed, vent and daisy still did not move. It was steady at 225, then just went up 100 degrees. I got it back down to 225 and kept going. Then in the 4th hour the temp dropped to 195F. Again it was steady, then just dropped. Again dialed it back up to range. After 5.5 hours, pulled the ribs off, they looked good, but ended up pretty dry. They had good flavor and a good smoke ring, but they were dry. The firebox was cleaned out before the cook, there were no blockages. Does anybody have any idea why the temp didn't hold. I'm new, but I don't think I should have to sit and stare at the thermometer for the whole cook. The dome thermometer has been calibrated as well. Help me out guys. Nothing worse than bad ribs. I'm trying again tomorrow. Thanks.