2nd reply try--Have done the same with a click release torque wrench.

Having access to the calibrators while working for a mega-corp,
First, a slow tug on the wrench does not allow the click-mechanism to release at the proper torque, normal ratchet speeds are needed. Easy does not do it!
Second, of my five wrenches, the worst was 5 ft-lbs low calibrated against a Mounds calibrator.
Third, the one wrench that was low was loaned to a pal for a long time who did not release the spring tension by setting it back to minimum.
Fourth, for more accuracy at lower torques, the 3/8 and 1/4 drives inch torque wrenches work so much more accurately.

TRIVIA- All space-craft and critical aeronatical operations mandate using a dial torque wrench that has a torsion beam, instead of a spring-plunger-cam, and internal works similar to a dial indicator. Three inch dials and movable stop pointers gives high accuracy. Similarly, digital wrenches changed the dial indicator a readout like on a digital caliper.