Slow to react to correct resistens during intervalls

im having problems when riding intervalls, the trainer is sometimes very slow to react to the correct resistens lvl between 6, and 12 sek, before turning either up or down resistens,,(its in ERG mode) rather fustrating on a 20 sek intervall,, and on a sprint effort, sometimes its stock on an xxx watt, when the effort increases,,,, any other tried these things