Sample stretch causes audio degradation?

Hello Isla friends! New to the S2400 and to the community, many thanks for allowing me to join… Noob question here: I have created a kit in the web kit creator and loaded them to a new project, but as soon as I started time stretching notes sequences - bass and organ and some chords too, mostly from 120 to 125 bpm, I immediately found out the quality of audio has gone very bad, without much top end and a little wobbly, any thoughts or advice on that?

Any help or comment appreciated, thanks in advance

PS: hi-fi engine used on all of them

What exactly do you mean by " time stretching notes sequences"? Is it a single sample? Time Stretching using the S2400 in Track Settings / Actions ?