I think I can help. The probe is on the first 4 sections then you added 2 more. Your stat is shuting off when the first 4 is hot enuff but the last 2 were pluged in while the others were hot so your stat is shuting down with the first 4 and not alowing the last 2 to catch up. I would try turning the stat off for alittle bit ( an hour or 2 ) Then let all 6 sections of heat tape heat up together. I realy hope this makes sence. Lol.