Is the current CL17 tubing made of a different material?
CL17 part information
Part way through 2014, the CL17, SP510, MO42 and Series 5000 Instruments and kits were shipped with new tubing. The previous tubing was a white, opaque material. The new tubing is a beige or tan opaque material. It is now made from neoprene. It should not cause any differences in readings.