Somehow i wasnt aware of this thread!
I am hatching with one of these, Still air
she told all about the thread Jack yer just too busy yappin you dont pay attention
you opened the top so it had to work longer to get the temperature back to where it was set meaning it had to run longer . the element continues to heat for two or three minutes after power is cut off to it . most temperature spikes are caused by room temperature rather than the incubator itself . that is why not near windows no direct sun light and a stable environment is so important. most of all with a still air . also why you don't open it more than you need to . sorry Should have been here . you will get a spike every time you open the incubator next one will be when you candle .