I printed with Filaflex Shore 82A without problems using slow speeds, a 0.6mm nozzle and a 3d printed connector, which closes the gap between hotend and exturder. The connector has to be placed on the hot end filament intake before the hot swap nozzle is inserted into the dual extruder.
https://www.printables.com/de/model/993227-snapmaker-dual-exturder-tube-connector-for-flexibl