What filament are you printing with? you mention flexible is it TPU? I've been experimenting with TPU and found retraction needed to be turned off, speed 15mm/s, Outline underspeed 100%, Solid infill underspeed 100% and turn on ->Advanced->Avoid crossing outline for travel movements. I also upped the extrusion multiplier to 1.10 rather then re-calibrate the extruder each time I use TPU.