Interval Workouts--- Resistance issues

I’m new to smart trainers and the apps. I have a Saris H3. I’m finishing my first evaluation of a platform (Rouvy), and attempted two power surge workouts… You start with a warm up (150-170), surge to 300% of that (600 about, 130cadence), then settle into an elevated level (170-185), surge to 300% of that (600 again, [115 max cadence] but kept it only for a short spell, because unwanted resistance kicked in, dropped back down to 170-185). On the third 300%er, the resistance was so oompossible, I was churning only 400, with cadence at 75 max, which ain’t gonna get you 600 power numbers. I also stopped the workout at that point, because the trainer was doing things that I did not want it to do.

I mentioned this in my post ride comments, and one of my riding buddies mentioned something called an ERG death spiral. I did a little reading on it, and it sounds like it might be the problem, but I’m not sure how to circumvent it and be able to have an interval workout without having all the unnecessary resistance, that I do not want in this type of workout.
Both power surge workouts ended prematurely, but doing Alpe du zwift, no problem!!!

Those of you that do structured interval workouts, is there a certain mode you put your smart trainer in so you can get to your 300% power numbers when the workout calls for it?
Does the problem lie with a setting on the H3?
Does the problem lie with the Rouvy app, and will I have this same problem using Trainer Road, zwift, bkool, etc? I’m trying to evaluate training platforms right now, and don’t want to be discouraged from doing structured workouts, which I do enjoy periodically.

Thanks for your suggestions.

If it is the death spiral, you can help the trainer a little by adjusting your cadence before an interval starts. So about three seconds before the 300% intervals, increase your cadence to something over 100. That will give you a head start on the power increase and the high cadence means you won’t suddenly be hit with insurmountable torque.

For short sharp intervals like that, you might prefer to do those portions of the workout in resistance mode (i.e., disable ERG). The important thing is to go all out for those 300% segments, it shouldn’t really matter what your power numbers are. By doing it yourself through gear and cadence changes, you won’t get bogged down by the trainer trying to find the appropriate resistance to provide.