Yes... possibly this: if that slider is shifting the curve by 15% of full adjustability range, over the entire range, then you are in trouble with anything below half trouble.
Because at full throttle (high end of the curve, where the values are high as well) 10 or 15% more or less fuel isn't that bad, it's a fairly decent range of adjustment.
But at lower throttle settings, where the curve is low, 15% more or less WILL kill your engine. Probably 5% allready will.

What you need to do, is set up the programming such, that the curve is fed to an unused channel (say, channel 17 or higher, one you do not have a servo connection for) and then set up S1 such that it affects the "weight" of that channel. Then link the output of that channel 17 back to the channel you hook up the solenoid to.

That way, adding 1% of fuel by means of the slider, will be 1% of the actual curve value that you are running at at that time.
Set S1 in neutral and set up a running curve on the ground. Go fly, and whenever you detect a spot on the throttle range where the engine is not running to your liking, you can carefully tune, for no other purpose than to determine whether that rough spot is lean or rich, return the slider to neutral (these sliders should have a tactile neutral position), land, and adjust the curve accordingly.

Be very careful when doing this, because airborne, "running optimal" and "flame out" are VERY close to each other, there is not much of a lean range between those two points, and at times, rich and lean are hard to distinguish by exhaust note alone. Therefore, when adjusting, ALWAYS first test towards "richer". If running improves, you were apparently in that very narrow lean range, if running deteriorates, you know you were running too rich.
A first adjustment towards lean because you THINK you heard a rich run, in case you misheard, will cause a flameout and a deadstick landing.