Can't get quantize/audiowarp to work on whole clip

Trying to learn Cubase quantization using all the new tooIs to straighten 20 bars of acoustic guitar originally played at 107-108bpm.

After many attempts, manual adjustment of warp markers in Audiowarp produced perfect results for 13 bars, then the markers disappeared and bpm shot up to 120+ for rest of clip.

Splitting the clip to edit the second half didn’t work. I guess Audiowarp prefers unedited clips??