I agree with CA, too fast. Flexibles generally don't print well (if at all) at regular print speeds. As well as lowering retraction, maybe turn it off entirely. Try a range of print temperatures too.

Last but certainly not least, can you show us your extruder? Most extruders have a gap between the drive gear and where the filament enters the hotend, flexible filament tends to buckle in this area.

It might also be worth checking if your hotend is a bit (not fully) clogged or jammed, as flexibles seem a bit more sensitive to resistance to flow in the hotend because of the aforementioned buckling issue.