We're had some success printing with Ninjaflex TPE. The trick was to slow the print down significantly so that the back-pressure wouldn't get high enough to make the filament buckle.
Ninjaflex TPE seems to be well made, but we also tried the Filaflex filament from recreus.com, and it was horrible. Worst filament I've ever seen. We bought two different colors and received a sample of a third, and all three varied from 3mm to 2.3mm over the course of about 150mm of length, making it totally unusable. Do not buy.