First off a lot of people have problems with aftermarket sensors and will not use anything other than OEM. That said your replacement sensors should be fitted with a paper spacer on the end of them, this is to ensure the sensor is mounted the correct distance for it to operate properly. If this isn't there the sensor could get damaged as soon as the engine is started. If your new sensors didn't have a paper spacer on them (I don't think aftermarket ones do but not sure) the fitters may have just tried to guess where the sensor should be and have it incorrectly set. The paper spacer part number is 5252229 from Jeep. The sensor should be mounted with paper resting on the fly wheel/drive plate and the bolt tightened to 7 Nm (60 in-lb).